How To Build
A Reliable
VW AERO ENGINE
By Rex Taylor
Foreword
It is the intention of the author of this book to lead you, the home builder through the many pitfalls
of deciding what to build, what parts to use, what parts and techniques to avoid, how to properly
assemble your engine, and perhaps most important, how to check each step as you go to assure that
you are right so far, before you proceed.
The methods used within have been used repeatedly on H. A.P.I. Engines and have been proven
by many hours of running in many engines. We do not intend to imply that all these various changes
necessary to convert the Volkswagen engine to aircraft use are products of our own ingenuity.
Many of these changes have been used by others long before we adopted them. We found them to
work for us and used them in our engines.
No one man or engine builder has all the answers or a corner on the inventiveness necessary to
keep up with the state of the art in aircraft conversions. There are many talented people with very
good ideas that work in every corner of the world, constantly chipping away at the problems of
making a Volkswagen an even better aircraft engine.
In the past twelve years we have seen these engines evolve from a simple conversion with little
more than a prop hub and a magneto drive (in fact quite a few were battery ignition), to a
sophisticated engine which has a lightweight accessory case, 45 amp alternator, starter, oil cooler,
and many internal modifications for reliability in aircraft.
Constant speed propellers are available now as well as the ground adjustable props that are rapidly becoming standard. We designed a carburetor called the "SuperCarb" that allows cockpit adjustable mixture control in flight, '*just like a real airplane".
Instrumentation in the average homebuilt is rapidly becoming more thorough with cylinder head
temperature gauges, many with probes monitoring on all four cylinders, becoming the rule rather
than the exception. Exhaust gas temperature gauges allow the pilot to set mixture for maximum
power to minimum fuel consumption at any altitude.
Perhaps most significant, and most important, is the changing attitude towards the conversion. It
is a fact that through the efforts of many who built, tried, and proved these conversions reliable,
then shared their ideas, that we have a wealth of conversion knowledge to draw upon.
The author believes that for the most part we are out of the basic stage where the basic question
was '*Will it work?" or "Will it last"; and into the area now where we are refining and improving
on a good basic idea.
1
There are, of course, different approaches to a solution of the same problem and the manner in
which "H.A.P.I." has dealt with various problems in some cases may be a little different than what
another engine builder has done. This doesn't necessarily mean that our methods are that much better or worse than someone elses methods. What we have done is put together in our engines our particular combination of conversion ideas which have been proyen to work reliably together in an
engine.
The author strongly recommends that should you embark on the conversion trail, using this book
as your guide, that you follow this guide completely and not mix other methods with the ones
described here. The engine you build will perform reliably and for a long period if you keep
everything in the combination described. A change could very well result in a disruption of the harmonious blend of changes we have now and could very well result in a loss of the very reliability we
are working for. In the words of some not so ancient prophet, "It works this way. Don't mess with
it!"
There is no reason why you can't build your own engine by following the methods described
here, step by step, and produce an engine that is as well built as any available.
The secret of a beautiful engine is very simple; you just put it together properly. "NEVER" I
repeat "NEVER HURRY", "CHECK and RECHECK" each and every step before going to the
next one. If you are not 100 percent satisfied that what you have just finished is done as well as it
can possibly be done, then you are not finished. One thing you should always keep in mind above
every other consideration is you will bet your life on this engine every time you fly behind it. Take
whatever time it takes to do each small job to perfection. You will finish your engine knowing you
can depend on it because you will be able to see each and every part in your mind secure in the
knowledge that you did it right. Therefore your engine will not let you down.
After following this book to completion you will know your engine intimately, and you will be
able to maintain and repair it from a point of expertise and ability. You will be free from a
dependence on a mechanic who many times is more interested in your money than your problems.
Best of all, perhaps, you will gain
a pride of ownership of "your"
engine that you could never buy.
Now let's get started building
you an engine!
2
chapter 1
before you start . . .
DECISIONS
The process of building up your engine is largely one of decisions. Since the ultimate use on your
aircraft will vary from builder to builder, your decisions along the way will have to be based on
what you want the end result engine to do for you. This will vary considerably from say a Jeanne's
Teenie to a KR-2 type aircraft. On the J.T., the builder may want to go very simple: hand prop to
start, no alternator, no accessory case, a simple wooden fixed pitch prop, single ignition via a
"Vertex" magneto in the distributor drive hole, and presto, you have an efficient, low cost
powerplant.
Our next builder, however, wants all the trimmings: dual ignition, alternator, starter, accessory
case with vibration damping motor mounts, cockpit adjustable propeller, turbo charger, and an oil
cooler system. Since he is installing this in a pressure cowling, he also wants the lower cylinder
shrouding which is the basis of the pressure cowling system installed as the engine is built.
Another pilot is building an airplane requiring a pusher engine installation, so he has some
specifications unique to his project that have to be worked into his decision making process.
Even before this engine decision ordeal starts, you should have already made quite a few decisions. Before you build a suitable engine for your aircraft, you should really study the design and
decide exactly what you want and expect from the engine in your airplane. If it is a bare minimum
airplane that flies well because of its lightweight simplicity, don't louse it up by hanging extra
weight on it. If you do, you will wind up with an airplane of marginal performance and possibly
marginal safety.
I remember a Smith Mini airplane at an airshow once: full I.F.R. panel, heavj radios, complete
electrical system, lights, stereo tape deck and C.B. radio. All the equipment you could imagine. It
was so heavy, and flew so badly, that even the owner/builder was scared of it. Yet there were
potential builders at that airshow who thought that was the most beautiful Smith Mini ever and
wanted one just like it. The point is, start out at the very first with the game plan in mind. If you
want to make changes to the design you are building, or add weight, you are going to come up with
3
something very different than the original. If you consider all the factors that contribute to good
performance in a lightweight aircraft, fight wing loading and light power loading are the most important contributors to good performance. So, have firmly in mind what aircraft you are going to
build, what power it is going to require, and if your ideas differ from the designers on the heavier
side, they are probably not as good as his.
So now it is time to start making your engine decisions. You have the airplane you want to build,
or may even have it near completion, and decision time on the engine itself has arrived. Probably
the first real decision is whether to build it yourself or buy an engine from those of us who convert
them as a business. There are good and bad points either way you decide to go.
If you go the factory converted engine, you will have to spend a good sized chunk of your aircraft
cost usually in one place at one time. Of course, you get an engine that you have not expended many
hours of labor on, but sometimes the wait with some brands of engines is a year or more before
delivery. Even purchasing a ready to run conversion, you will still have to do a lot of installation
and cowling work which is really part of the powerplant. The big advantage to buying a factory
conversion is that a certain wealth of Volkswagen conversion experience is built into the engine.
Some conversions are better done than others, and the more time spent in comparison shopping
when purchasing one of these conversions the more likely you are to get the reliability and performance you are looking for. The porfessional convenor has probably gone through an extensive test
run period and has engines in use in various aircraft. He has had the input from his customers concerning problem areas, so that he has probably worked out most of the bugs in his conversion
design.
Another important factor worthy of your consideration is the area of warranty or guarantee that
you get from the conversion manufacturer. Most legitimate engine builders will stand behind their
engines to some degree should you have trouble with one of them. Should you build your own, you
become your own guarantor and will be totally responsible for any problems that may develop.
The question that quite naturally comes to mind is whether or not you, as an inexperienced person
in the area of Volkswagen aircraft conversions, can manufacture and assemble an engine that has
the same degree of reliability as one you can buy. I think the answer to this question is a definite
yes, if (and here comes the rub) you have or can develop all of the following essentials:
1) A clean, dust free place to work on your engine.
2) Proper tools to perform each stage of the assembly.
3) Reference material available to guide you through each operation, and assure it is done properly.
4
4) The machine shop tools, or machine shop services available for the necessary machining.
5) The patience and study time necessary to understand each step before you start it. Then do it, and
possible re-do it, until it is right.
If you have these five things going for you, or at least most of them, you can build your own
engine. On a cost saving basis, if you put a reasonable price per hour on your time it will probably
cost you more to build your own engine than to buy it. In terms of pride and accomplishment you
will gain an understanding of your engine, and indeed may well find that working on engines is a
very enjoyable pastime. Most of the things you will be exposed to will help you in tinkering with the
family automobile.
If, however, you are an impatient person who does not enjoy working to exacting tolerances, or
do not like to get your hands oily, or perhaps you are one of those people with a "that's good
enough" attitude who is satisfied with less than perfect in the jobs that you do accomplish, do
yourself a favor and buy an engine! There is only one way to build an engine properly. That is to
build it the very best it can be, or do not do it at all!
Now let's look at each of these 5 essentials in order to clarify them:
1) The clean, dust free area need not be large. A small corner of your garage should be sufficient.
I will assume you have a sturdy table at a comfortable working height to work, and probably a
bench vise. Two very useful tools in the building of a Volkswagen engine are an engine buildup
stand, which holds your engine in any position while you work on it, and a plain drip pan such
as is used under automobiles to catch dripping oil on garage floors. The pan is used on top of
the bench as your spotlessly clean surface for building up sub-assemblies and laying out your
tools. Incidentally, your tools should be cleaned in solvent, dust and dirt free before using them
on your engine. It is a little like a surgeon operating: the work area must be free from contamination by dust and dirt.
Since this process will undoubtedly take a few days spare time at the very least, your engine
and its parts will require protection from dirt during storage periods. We have found that plastic
garbage bags do an excellent job as dust covers capable of enveloping a complete engine on its
assembly fixture and really protecting it from dirt until the next time you can work on it.
2) The tools required to build up your engine will require an investment of possibly $150.00 if you
don't already have them. You will need a 3/8 drive socket set and a set of box/open end
wrenches in metric from 10mm to 17mm sizes. You will also need a ring compressor,
screwdrivers, pliers, alien wrenches, and most important of all an accurate torque wrench. If
5
you think you can guess your way through
and avoid buying a torque wrench, forget
building an engine at this point. You don't
have the right attitude, and you are going to
produce a piece of undependable junk.
Either condition yourself to do the job
totally right, or don't do it at all. You will
require a few more tools such as a propane
torch, possibly a gear puller if you have to
pull your prop hub for some reason after assembly, a dial indicator, a 2 to 3 inch micrometer,
and an OHM meter for timing your magneto.
Liberate some of your wife's
baking pans to store your nuts and
bolts as they are removed from
your engine. Separate them into
engine sections, such as head
bolts, crankcase bolts, internal
engine parts, etc.
3) The reference materials needed
will hopefully be entirely met by this
book in the subsequent chapters in the
step by step assembly section. There are some other publications available that can add to your
reference library, such as the type II engine maintenance manual available at your Volkswagen
dealers. If you are a person who has never had much experience in engines, I suggest looking in
the public library for a good book on a 4 cycle engine theory and operation since basically all 4
cycles are very much alike.
4) The machine shop services, or machining ability and availability you will find necessary, are
probably the largest stumbing block for some of you who live in the areas of the country where
Volkswagens are not quite so common as they are in California. There is quite a bit of
modification and machine work necessary to build anything larger than 1680 C.C.'s. With the
larger bore sizes, the engine crankcase and cylinder heads must be bored out to accept these
larger assemblies. While the operations necessary are not too complex or difficult to do, to
have them done in a shop that has no previous experience with these operations usually proves
very costly because the shop would have not developed holding fixtures and cutting tools to do
6
it in an efficient manner as in a production run. The shop will charge you by the hour, usually,
and it will be very expensive.
There are many firms who do -is work on a routine daily basis for very reasonable prices and
turn out good quality work. Some of you in these areas mentioned may have to send your parts
off for machining.
Should
you be fortunate enough to have your own lathe and milling machine, or access to one, you may
be well able to perform these jobs yourself. There is one point to consider here; if you louse it
up, you have to throw it away at your own expense. But, if the shop louses it up, they must
replace it at no cost to you!
5) The last requirement is the most important of all. Those of you with patience, dedication to the
task at hand, and the will to finish, can probably get by very well without having the most ideal
conditions to work in, the best tools to work with, abundance of reference materials for every
question, and the availability of an expert machinest or machine tools of your own. If you are
not willing to spend the time necessary, or don't have a good track record for finishing projects
you start, you probably won't finish this one either. If you don't finish and decide to sell out,
you'll probably take a considerable loss on your investment in parts. So be honest with yourself
about yourself before you start.
By now you should have decided what your engine needs are for your particular airplane, but you
still have some more decisions to make. We can start building up an engine based on all new parts,
or we can use a certain amount of used parts in the process. Either way it has advantages and certain
disadvantages. New parts of course are more expensive, but are many times easier to get and you
do not have to clean years of accumulation of grease and dirt before you use them. Used parts are
sometimes obtained very cheap if you are a good scrounger, but you never really know what you
have until you have spent hours in tear down, cleaning and inspecting for damage that will render
the part incapable of being rebuilt to aircraft standards. Sometimes you will get lucky and get an
engine that is very good inside. Then there are the others that turn out to be junk. In which case you
have usually wasted your money as most used parts are sold on an "as is" basis.
If you plan on going the used engine route, don't get in a big rush to buy. Look around the auto
wrecking yards in your area and try to find a Volkswagen that was wrecked rather than one that was
run out. Look for one that was totalled for front end damage with the engine and transaxle section
undamaged. The transaxle is not important to us, but if it is damaged there is a good chance that the
engine case has had severe shocks and stresses too and is probably also damaged. Many times cases
7
are cracked in accidents. But such cracks are not found until after the engine is disassembled and
cleaned.
Your best bet is an engine that can still be started and run in the car. The engines found in the
Volkswagen squareback sedans and stations wagons that Volkswagen calls "suitcase engines" are
a very good source for aircraft. These engines were all built in 1500 C.C. or more displacement,
and most have the desirable large oil galleried case. Best of all, they are not as eagerly sought as the
vertical blower bug engine, so usually can be bought for less. Some of the later squarebacks had
electronic fuel injection and dual port heads. The fuel injection is of no value to us, but the rest of
the engine is very suitable for conversion. This engine is an ideal choice if you are going to build a
turbo-charged engine.
In the rear of this book you will find a list of engine identity numbers, and the most desirable for
our purposes are underlined. Also given are some of the means of identification between the various
cases and other parts you will need.
New parts, of course, are much easier to obtain, but even here you will have to know exactly
what you want and be sure you are getting what you want. There are all too many suppliers of
replacement parts for Volkswagen now who are turning out parts that look like the original, but are
real junk. In order of quality, the best parts are usually German, the next best Japan, and the real
junk is from Brazil. This is not a hard and fast rule, however, as each of these countries mentioned
also turns out some parts of very good quality. The super bargain Volkswagen parts you will see
advertised in some catalogs are usually very shoddy quality even for auto use, and are poison in an
aircraft. Price alone is not always a good indicator, but is a fairly reliable one.
We have been offered a set of gaskets for as little as 93 c , but we still use the gaskets that cost 5
times as much simply because we want the oil on the inside of the engine. The Volkswagen gasket
set consists largely of rubber seals, and you want a high quality, live, heat resistant, long life rubber
instead of hard, inflexable, dry junk in the cheap sets offered. If the parts you buy will not do the
job properly, they are not cheap even if you get them free.
There is another source in the form of rebuilt parts. They are rebuilt cases, reground crankshafts,
rebuilt heads, and even rebuilt connecting rods.
The rebuilt cases can be a good alternative source to a new case if they have been aligned, bored
and reconditioned by a reputable firm who has high standards. A reconditioned case can serve you
as well as a new case. The big question here is to know what kind of an outfit you are dealing with.
8
One such company is Rimco whose cases are equal to new in reliability, but "low" in cost. The
sharp person will see right away how Rimco gives you a straight job. True main and cam tunnel
align-boring.
The sharp person will see right away how
Rimco gives you a straight job. True main
and cam tunnel align-boring.
Cylinder heads are routinely rebuilt for auto use, they are rebuilt with salvage methods such as
helicoil inserts in the spark plug holes. Cracks are repaired by heliarc welding, which is asking for
trouble in aircraft. You may find a pair of heads on a used engine with none of the above problems,
but be aware that the used engine you buy may have already had less than airworthy things done in
their past history. New cylinder heads are not too much more in cost than a top quality rebuilding
job, and you can be certain of what you have.
Crankshafts are a different matter. Used ones are the best within certain limits. For many years
Volkswagen built their engines with a high quality forged steel crankshaft that has bearing journals
surface hardened. These shafts are readily available, and most will be found to have serviceable
standard size bearings. Such a shaft, after magnafluxing, is reground to .010 undersize on the rod
and main bearings, and will be far superior to the soft cast steel late model cranks for use in aircrafts. A cast crank when subjected to bending or shock loads is brittle and will break like a piece of
glass. A forged crank will bend without breaking. A broken cast crankshaft could easily result in
loss of your propeller. The 1500 crankshaft V.W. parts #311-353-A is our choice because it has the
cross drilled oil feed holes to the bearings, but it does not have the elongated slots like the later
cranks. The bearing loads imposed by aircraft service cause the elongated slot cranks to wear out of
round due to the smaller amount of bearing contact surface.
Rebuilt connecting rods are cheap but should be avoided as there are too many things that can be
9
wrong with them that may not be apparent on inspection. We use a very expensive rod by comparison but have never had a connecting rod problem of any kind. We feel the extra expense is
justified.
Most of all the remaining parts in the engine you build will be new except for those stock parts
that are used in the non-critical areas on the engine. We will look them over carefully to ensure their
airworthyness in the step by step chapters.
PROP HUB ASSEMBLY
The other parts that are unique to the
Volkswagen conversion are the propeller
hub and the various castings or machined
plates necessary to cover up or alter the
function of the various openings in the
Volkswagen crankcase.
You will also have to decide at this point
on just what kind of conversion you want to
build and how simple or complex you want it
to be. Should you want to go full house of
engine accessories and add the turbo
charger, your engine will become a much
more complex piece of machinery where interrelationships between such things as compression ration, boost pressure, and engine timing are
critical to performance, and if not right, will tend to self-destruct. Conversely, the ultra simple
engine is relatively easy to build, though it requires equal exacting attention to detail, there are not
nearly so many details to keep control over.
Probably most designers would be very happy if the builder would stick to the simple versions
because of their lighter weight in the aircraft. All other things being equal, the light aircraft will
always out-perform the heavier one. The builder should bear in mind that while the starter, alternator, accessory case is very nice, it does require the use of a voltage regulator, battery, battery
cables, ammeter, master switch, master relay and usually a few more goodies. The total added
weight to your aircraft will probably be over 25 lbs. Should you want to add the turbocharger on top
of this, figure another 30 lbs. for the turbo and its complex manifolding. All of this weight we are
talking about here is usually concentrated on the nose of the airplane, and many times requires moving the engine forward to cram all the goodies under the cowl. So, not only do we have a lot more
weight up front that the engine designer never figured on, but we have it farther forward to com-
10
plicate the problem of center of gravity even further. The sad part of this weight problem is that
none of the accessories have added in any way the horsepower available, and your airplane will
know it when it comes to lifting off the ground.
There is an all too common misconception that the turbocharger will somehow
boost the power to earth-shaking levels,
Kajay turbocharger internal configuration is shown
in this display cutaway.
and that is pure fantasy. The only purpose
of the turbocharger on a Volkswagen conversion is to allow sea level atmospheric
pressure at the higher elevations. For instance, the airports around Denver Colorado are usually above 5500 feet in
elevation. In this situation, the turbo is
used to boost to sea level pressure, say 30
inch manifold pressure, in order that the
engine can deliver its full rated power at
the higher elevations. It is true that the
turbo can also be used to boost manifold
pressure to as high as 60 inches and greatly increase the horsepower at the propeller. But to use the turbo for this purpose is a very dangerous practice that can blow your engine
real fast. Those of you who build turbo engines should realize at the outset that boost pressure is
destructive. More than 5 inches boost will shorten the lifespan of your engine to a fraction of what it
should be. There is lots of boost pressure and horsepower available by just pushing the throttle
open. Since our systems have no automatic waste gates or pop off valves, watching the manifold
pressure gauge is our only reference. Some turbo pilots fall into the habit very easily of overboosting. The first time they may over-boost to increase speed on a fly-by to impress friends. Then
they start doing it routinely. Then they figure their engine takes 5 inches boost no problem, so they
boost 10 inches on the fly-bys' until one day the engine simply can't take any more over-stressing,
and lets go with all its expensive goodies. Flying the turbo engine calls for a large dose of selfdiscipline in the throttle pushing department, and if you don't have the self control to exercise it you
are "GONNA BLOW YOUR ENGINE!" We do not object to the use of 5" boost pressure or 35"
of manifold pressure on our own turbo charged engines, but such boost should be used only on takeoff and "limited" to 5 minutes duration. It is absolutely necessary to have the turbo engine well
11
monitored with exhaust gas temperature gauge and manifold pressure gauge mandatory. You
should also have a carburetor that allows mixture control, and an oil temperature gauge.
The process of combustion is one that generates heat in direct proportion to the amount of power
developed. If we use the turbo to generate more power even in very moderate boosts for short duration, the extra heat must be dissipated. You may have to think about and install cock-pit operated
cowl flaps on your airplane to allow more cooling efficiency at high power settings. Since these settings are used at low speed and high angles of attack, such as take off and climb out, the very time
when we generate the most heat is when our cooling systems have the least effectiveness. What all
this adds up to is the fact that when you choose to go to the more complicated engine for either luxury of the self starter and alternator or the extra power availability of the turbo, you must realize
that much more weight and system complexity must be expected in airframe also.
The ultra simple conversion can be and
usually is the most powerful engine on a
pound per horsepower basis. We can
build a simple engine with as much
displacement
and
torque
as
its
sophisticated counterpart. In fact, there is
no real difference in basics, just the difference in what we bolt on after the
necessaries.
There is one area where we can get a
solid horsepower increase without harming the engine nor going to great expense.
This is in the exhaust tuning department.
To understand exhaust tuning, we should review what takes place inside the combustion
chamber. Let's start with the intake stroke. The intake valve is open and the piston is on the
downsroke creating a vacuum inside the cylinder. Now, it's not really a vacuum in the outer space
sense. It is, in fact, a pressure differential, but we use the term vacuum in this case. We also have
atmospheric pressure forcing air through the carburetor, which is mixing fuel into the intake
manifold and then into that cylinder vacuum. All of this occurs because where there is a pressure
differential air will always move in a manner to equalize the difference. Under optimum conditions,
this would charge the cylinder at the bottom of the stroke with a cylinder full of air-fuel mixture
ready for the compression stroke. That condition would be full atmospheric pressure. In practice,
12
however, this ideal condition is impossible to achieve because the intake valve closes slightly before
the piston reaches bottom dead center. Therefore, the cylinder has not reached optimum pressure
equal to atmospheric pressure. So we have the piston ready to start the compression stroke but must
move up the cylinder a certain distance before that atmospheric pressure value is reached and actual
compression of the air-fuel mixture can start.
* See below for diagram of 4 cycle operation.
As you can see, anything that can be done to get a better vacuum in the cylinder, or more atmospheric pressure, will result in a greater volume of air-fuel mixture at the bottom of the intake
stroke. The more air-fuel charge we can cram into the cylinder, the more power we can develop
with each firing. There are many ways to increase the size of this charge. Most of us are familiar
with the old single barrel carburetors on our automobiles. Then came two barrels, and now the
modern auto uses 4 barrels with progressive linkage. The main purpose of this is to really open up
the intake manifold to allow atmospheric pressure to charge the cylinders quickly, and with the
largest amount of fuel-air mixture possible. It is more difficult to charge the cylinder efficiently at
high RPM's than at lower speeds, because air, being a fluid, tends to remain in the state it is
presently in; either in motion or still. Since we are alternately starting and stopping this movement
of air-fuel into the cylinder with the intake valve, when the valve opens the air must again start
moving from a still condition.
A.
B.
C.
D.
Simple four-cycle engine
Intake Stroke - Fuel/air charge is drawn through open intake valve.
Compression Stroke - Charge compressed with both valves closed.
Power Stroke - Charge ignited by spark plug pushes piston down.
Exhaust Stroke - Burnt gases expelled through open exhaust.
13
It might be well at this point
to spend a little time discussing
turbo charging, since having
understood the charging process
makes it easy to see what turbo
TURBINE
SECTION
charging does for us, and why it
can increase power available to
the self-destructive point on
your engine. The turbocharger
is really a very simple gas
driven turbine. It is mounted on
the engine's exhaust system is
such a manner that the exhaust
gases must pass through and
COMPRESSION
SECTION
spin the little turbine wheel on
EXHAUST GAS IN
their way out of the exhaust
pipe.
Cross section of typical turbo.
This extracts a con-
siderable amount of otherwise wasted energy, and we use this energy to power another turbine that
compresses the intake air-fuel mixture in the intake manifold to pressure as high as 60 inches of
mercury, or roughly twice the atmospheric presure.**
Now with this greater pressure inside the
Exhaust
manifold, it can be readily seen that we can
stuff a lot more air-fuel into the same
cylinder. In fact, what happens is that we
Intake
can not only fill the cylinder, we can fill it to
the point of pressurizing it at the bottom of
the stroke to very high pressures. If we were
to run 60 inches manifold pressure, or
roughly twice the atmospheric, we would
pressurize the cylinder at the bottom of the
stroke with twice as much air-fuel mixture as
normal. This downward intake stroke of the
piston does in fact become a power stroke at
** The turbo chargers and pressures described here are those common to Volkswagen conversions. Others may have different
capabilities.
14
boost pressures because the boost pressure is actually pushing the piston down on the intake stroke.
The cylinder at normal atmospheric pressure, which has a compression ration of 7.5 to 1, will have
an effective compression ratio of 15 to 1 due to the boost pressure. The mixture is then fired at the
top of the stroke at about double the normal cylinder pressures. Is it any wonder the engine can't
take this kind of heat and pressure for long? We have not even talked about the tremendous bearing
loads imposed on the crankshaft and connecting rods. The exhaust valves are subjected to twice as
much hot gases to remove from the cylinder with each exhaust stroke so they are very apt to fail.
One very important aspect of turbo charging that contributes to their efficiency is the fact that the
pressurized incoming charge of fuel tends to push the last remains of the burned gases left over
from the previous stroke out of the cylinder so that the fresh charge is much less diluted by burned
gases, and consequently delivers more energy when fired.
The late automobiles equipped with turbos also have automatic waste gates controlled by a solid
state mini computer that is designed to outwit the ignorant driver who would perhaps "get his foot
in it" and over-boost to the point of engine damage. The computer senses this potentially damaging
condition and diverts the flow of exhaust to bypass the exhaust driven turbine, thereby controlling
its power to destroy the engine.
Our little aircraft is not so sophisticated as to have these computerized waste gates, but if you use
the computer between your ears to control the throttle pushing hand the same degree of effectiveness can be achieved.
There is another area for boosting horsepower by charging the cylinder with a less diluted larger
volume charge that offers much if the same advantages without the potential for destruction and is
much less expensive. Tuned exhaust systems are based on this principle, that a fluid in motion tends
to stay in motion. If you were to take a long piece of exhaust pipe and give it a quick hard blast of
compressed air in one end, then instantly cap off the end, the air rushing through the pipe would, in
its tendency to remain in motion, actually create a vacuum in the now capped off end in the tube.
The tuned exhaust system works on this very principle, in that the out going high pressure, high
velocity exhaust gases will pull a vacuum in the cylinder that will help to scavenge the burned gases
out and get maximum effectiveness out of the fresh charge. There is a certain period of time at the
transition point between the exhaust stroke and the intake stroke when both intake and exhaust
valves are in the open position which allows this scavenging action to take place. This is called
valve overlap. The length of the exhaust pipe, diameter, amount and radius of the bends, interior
surface roughness and other factors are all involved in the tuning process, which is only really ef-
15
fective in a very narrow RPM range. In aircraft, our power range is narrow anyway so exhaust tuning is somewhat easier.
The theoretically perfect exhaust pipe in an 1835 C.C. Volkswagen would be 1 1/2 dia. pipe 84 inches long on each cylinder, and the pipe would have no bends. This would be a full wave system.
HAPI' S system is built on the half wave length of 42 inches, which is less efficient, but we feel is
the best compromise between weight and efficiency.
There is no way the tuned system can harm
your engine. It merely lets the normally
aspirated engine work much closer to the
theoretical 100% efficiency that of course is
never achieved. Tests indicate the tuned exhaust system does provide from 5% to 12%
more available horsepower at the prop. The
tuned system is tucked around the engine to
take up very little space, but does weigh an extra eight pounds over the weight of an engine
with the little short straight-out exhaust stacks. Again, you have to decide whether the extra
horsepower you can gain is worth the extra weight it will add to your aircraft. It seems as though
everything involved in the aircraft usually is slightly less than ideal, but is the best combination of
the least compromises available. When you start this decision making process, have a firm idea of
the goals you wish to achieve and carefully consider each and every factor. If you do this, your end
result engine will serve you in the manner you expected when you started.
16
chapter 2
NEW or USED?
Now that you have nailed down the specifications of your engine and have a clear picture in mind
of exactly what engine to build to do the best job, you have to make some more decisions.
The first of these decisions involves whether to buy a used engine and rebuild it into an aircraft
engine, or to buy new cases and heads and build from there. Some of you may feel that you save
some bucks by going the used route, so we will now discuss what to look for and avoid when buying
such an engine. We discussed in an earlier chapter the best probable sources for a used engine short
of stealing the one out of your good wife's car. Now we have our cherry used engine sitting on the
workshop floor, and we must find out what parts are good quality rebuildable parts and what parts
won't make the grade. The first thing to do is to get the thing spotlessly clean on the outside, and all
the oil drained out of the inside. An easy way to clean one of these messy things is to take it to a
coin-op car wash and knock all the accumulated grime and grease off the outside with high pressure
hot water and soap. Don't be afraid to turn it upside down to clean it, or whatever it takes. If water
and soap get inside it, it will not hurt " I F " you are going to tear it down in 48 hours or so. Otherwise try to keep the water out to avoid internal rust. When it is really clean, take it home and put it
on your work bench on the metal tray. If you want to do the job right, do yourself a favor and buy a
Volkswagen assembly stand. It bolts on your work bench and onto the engine to allow you to work
on the engine in any position by simply rotating and locking it in place.
(See photos in assembly text for stand use)
If you have ever built an engine without a stand, then one with a stand, you would agree that it's
as necessary as the rest of the tools. It costs about $35.00 and is well worth it. If you bought a stand
and have it on your bench, bolt your engine to it and put that drain tray on the floor under it to catch
the crud that will drip and fall as you disassemble.
First, remove the rocker arm covers, oil sump cover and screen. Stop here and take a real good
look at the screen. Since you are going to throw it away anyway, don't worry about destroying it.
Take it apart and look for metal particles inside the screen on the sheet metal bottom. If it is free of
metal this is a good sign; though it might simply mean the screen was just changed just before the
17
car was junked. If you find metal particles, or other trash, you know something inside the engine
was shedding metal.
Now let's remove the heads. A wise mechanic will loosen all the headbolts a half turn or so
before starting to remove anything. The first half turn is to relieve some of the pressure on each stud
and not wind up with one stud trying to hold too much pressure and stripping threads in your case.
Look out for old studs that are bigger in diameter than the others. If you run into these they are
usually a patch-up job to fix threads already stripped out of the case at some previous time. After
the heads are removed set them aside for a close inspection later. AJ1 you need now is to assure
yourself that there is no catastrophic carnage in the combustion chamber area; such as a broken
piston, dropped valve, or some very obvious problem.
The next thing you need to do is remove the flywheel and pulley on the other end of the crank. To
do this you will need 2 large 1/2 " drive sockets (one 30mm and the other 36mm plus), and a 1/2"
drive breaker bar. The flywheel is usually torqued to over 200 foot lbs., so you will need a flywheel
lock tool to hold the flywheel stationary while you loosen the gland nut. This tool sells for about
$9.00 or so. Remove the gland nut and the pulley bolt from the other end of the crankshaft. Put 2
large screwdrivers behind the flywheel 180° apart, and gently but firmly rock the flywheel off its 4
pins. Save the pins and the flywheel. Remove the pulley in the same manner.
Next, remove the cylinders one by one pulling them off gently so the piston and rod assembly
doesn't bang into the case as the cylinder comes off. When you have removed all 4 cylinders,
remove the wrist pin clips from the pistons. Find a round hard piece of wood (3/4" dia. dowel is
great) about 6'' long and use it to drive the wrist pins far enough through the pistons to free them
from the upper end of the rod. There is a potential for damage here to the rods so let's learn how to
do it right in disassembly, then not screw up a good new rod on assembly. When driving these wrist
pins, either out or in, never allow force of the hammer to be transmitted to the rod. Avoid this by
placing your hand around the piston on the side opposite the hammer side and gently tap the wrist
pin out while all the shock is taken up by the piston holding hand. Never let the piston lay against
the rod so that the driving force could possibly bend the rod. Correct rod alignment is essential and
can be lost by one careless hammer tap.
Now we have removed the pistons and have all the other goodies removed from the outside case
with only the actual case bolts left holding this engine together. Remove all the small nuts and bolts
around the outside case. There is one that many times is hidden under a layer of dirt and grease. It is
located on the flywheel end of the engine about 1" below the bottom large nut in a kind of a well
casting. "Be sure it is out!" If in doubt, count all the small bolts. There are 15 of them to remove.
18
Now remove the last 6 large bolts holding the case together. NOW CHILDREN PAY CLOSE ATTENTION, because a lot of cases are junked right here by people who try to pry them apart.
This bolt is the
first tightened
on assembly.
Case is doweled at "+" locations. Case can be
bumped with wooden block at darkened locations.
DON'T FORCE IT'.
Turn your engine stand so the case split line is vertical. You will note that there are certain areas
on the engine (see sketch above) where some tapping with a hammer and block of wood will not
harm the case. NEVER, NEVER, NEVER attempt to separate the cases by driving screwdrivers or
any sort of wedge between cases. Volkswagen uses precision machined surfaces with no gaskets,
and you can destroy a case by using improper tools. Take your hammer and wooden block and rap
cases at the points indicated going from one area to the other to keep cases opening evenly. When
the alignment dowels are free (case will open about 3/8") turn the engine on the stand so the half
with the main bearing thru bolts is down, and lift off the upper half of the case. Sometimes the
crankshaft assembly wants to come with the top half. Just keep wiggling everything, but NO
FORCE, and it will all separate. Now lift out the crankshaft and camshaft. Look for the small dowel
pins in each main bearing saddle. There should be one in each bearing saddle on the stud side of the
case. Save these dowels, you will reuse them. Take your crankshaft and set it upright on your bench
using the flywheel as your holding fixture.
Makes a very handy way to work on the crank. Now remove the rod bolts and all the rods. Pull
the old cam followers out of the case and throw them away. The four cam followers in the top half
of the case probably went on the floor anyway. Also discard the pistons, pins and cylinders. Most of
19
the valve train we will use if it's good, except the valves, guides, springs and keepers which we will
replace.
Now before you go any further, you need to know if you have a rebuilder or a piece of junk!
The crankshaft is measured with your 2-3 micrometer. Standard size on the rods and mains is
2.165". If your crank measures less, probably 2.155" or 2.145", it is already a regrind. If it is
2.165" and showing some wear, but no damage or serious out of round condition, it will regrind to
2.155" and be a good airworthy crank. If it is already ground, better just forget it and replace it
unless it is 2.155" and perfect in every way, which isn't likely. You will not be able at this point to
measure all the journals because disassembly of the crankshaft requires an arbor press to remove
the timing gear. Usually bearing failure is at the #2 main or one of the connecting rod journals.
First thing you will have to do requires the use of an arbor press to remove the distributor drive
gear and timing gear from your crank. This job can be readily done by any automobile machine
shop as it is common to American auto engines. While your crank is there, have them measure the
rods and mains to be sure they will clean up at no less than .010 undersize. You should have a crank
magnafluxed before you spend much time and money on it to be sure it has no hidden flaws. If
magnaflux is not available, there is a very simple test that can be performed to check for cracks.
Suspend the crank by a piece of wire and tap it lightly on a non-machined surface with a hammer. It
should ring like a bell. A cracked shaft or a cast steel shaft will give out only a "dull thud" sound
and both are bad news!
Now we still have to inspect the crankcase. Take if off the engine stand and wash it so clean inside and out that you could eat off of it. If you had metal in the screen you probably have trouble in
the case. Check for cracks first, especially if your engine came out of a wrecked car. These
Magnesium cases are on the brittle side, and while strong, will crack under certain stresses. Some
of the things to look for are broken ears where the oil cooler bolts on, main bearing saddles that
have had a bearing spin, and thereby ripping out the dowel pins and enough metal to junk the case.
Check for stripped threads around the oil screen cover plate and check cam bearing saddles also for
excess wear and damage. Some of the older cases did not have cam bearing inserts, but ran the cam
directly in the case material. I personally don't consider this case a real good one for aircraft unless
it is new or has very low mileage and wear.
If your case is still satisfactory, now take it to a competent Volkswagen experienced automotive
machine shop and have the main bearings checked for size first. If the size is such that the case will
clean up at .020 oversize, you are in business. If, however, it will not clean up just take your lumps
20
and write that case off for aircraft use. Any case that is to be rebuilt for aircraft should be alignbored. Volkswagen cases tend to wear in the saddle surface that is in contact with the outer side of
the main bearing shells. If this wear is not taken care of by align boring, new bearings will not be
held in place with the proper amount of "squeeze" and consequently you will have excessive
clearance in the mains even though the bearings are new. This is one of the areas where too many
poeopie will attempt to cut the cost of rebuilding by omitting the boring operation and a very short
time later be rebuilding again because the bearings didn't hold up in service. The crankshaft and
bearing loads imposed by aircraft service are much more severe than automotive, so don't use
anything of questionable quality.
Our other main area of concern is the cylinder heads which can't be adequately inspected until
you have gotten quite a bit of labor time in them. They must first have the valves removed. They
should then go into a hot tank to remove grease and grime (unless you really got them clean), then
be glass bead blasted to remove all the carbon build-up in the combustion chambers before you can
see what you've got. The two most common problems on Volkswagen heads are stripped threads in
the spark plug hole and cracks in the heads. Cracks may be most anywhere, but are usually from the
exhaust valve seat to the spark plug hole, or radiating out from the valve seat in some other direction. Another common place for cracks is in the boss around the exhaust valve guide. Other problems you may run into include bad valve seats that need replacing and heads that have had previous
cracks welded up. It has been my experience that used heads usually cost almost as much as brand
new heads by the time you clean, inspect, install new guides, regrind seats, and do other required
work.
The camshaft is usually found to be serviceable, but here the question is whether it is the proper
grind to produce the torque in the power band we want. It can almost always be reground to special
aircraft grind, such as our C-60 grind.
As you can see from above, there are many pitfalls to spoil the dream of getting a good engine for
a small outlay of cash. It does happen more often than not, but the odds are about 1 in 4 that you will
have to replace a good part if not all of the "rebuildable"? engine that you bought!
Over several years of experience with Volkswagens we have found that what we saved on used
parts usually was lost when we bought something that would not perform, and we had to scrap it.
There are many sources for new parts, with your local Volkswagen dealer being both a reliable
and very expensive place to buy parts. While Volkswagen parts are genuine, there are also genuine
Volkswagen cases and heads sold through non-dealer channels that are much more reasonable to
21
purchase. There are also some heads from Japan that are good, but they are not genuine
Volkswagen parts. Cases are only made by Volkswagen due to the tremendous cost of tooling up
for such a casting then machining it. There are genuine cases available at Volkswagen Brazil and
Mexican plants, and they are imported and sold by many non-dealer outlets.
HAPI can supply new cases and heads to those of you who need them. Even with a brand new
case and heads you are not home free. While we have never seen or heard of a bad case or head
from the factory, the cases and heads do require a couple of hours work to deburr the rough edges
left after machining, and to remove the flashing from the die casting. The German made cases were
out of these same molds, but the hand work was completed and cases were ready to use when you
got them. New cases come coated with a vasoline-like grease that keeps the magnesium from corroding after contact with the air and are individually boxed. One advantage in buying a new case is
that they now are cast with steel inserts in the case which eliminate the old problem of head studs
pulling out as long as proper torque values are used.
New heads should have the exhaust valve guides replaced with bronzanium guides then the exhaust seats reground to those guides. We have found that a 1/16" contact surface with our stainless
exhaust valve works well.
There is a long standing myth that Volkswagens are prone to valve problems. In fact, the valve
system is very trouble free when the heads get enough air and oil to cool properly. Of course, there
are other factors that can contribute to overheating, such as too lean mixture and improper timing,
but the basic valve train will give very good service if not subjected to abuse.
When it comes to crankshafts, we like the old ones. We like to use the shaft that Volkswagen used
on the 1500 C.C. engine in the late 50's. This shaft is a high quality forging, has large oil feed holes
to all the bearings, but is not weakened, as were the later cranks which have large cross-drilled
journals and elongated oil supply holes that greatly lessened the bearing contact area. The racing
crowd found that these older shafts were the most reliable under hard use, and we have had no bearing problems what so ever with this shaft. Perhaps best of all, they are still plentiful. Most ar standard size so we can regrind them .010 - .010, taper them for the prop hub and presto, an inexpensive, available, and reliable crankshaft.
So there you have the basis for your decision on the key parts of your engine. We'll talk about
balancing in the next chapter, and then start putting all the goodies together.
22
chapter 3
BALANCING
In the process of building an engine we are concerned with the round parts being perfectly round,
such as the bearings and cylinders. We are also very concerned with keeping the flat parts flat, such
as the mating halves of the crankcase and the head to cylinder seal area. Many of the necessary
operations to attain the above, the amateur can do in his limited workshop with a limited amount of
tools along with a plentiful amount of time and care. In fact, he can do as well or possibly an even
better job than a professional.
There is one area though
where we must go to the professionals
because
the
specialized
tooling
and
knowledge is beyond the
scope of the amateur or even
most
automotive
machine
shops. In this area we will
begin tuning the engine's individual parts by precision
balancing even before we
start to assemble the engine.
Balancing is a process whereby we equalize the weight of
all of the rotating parts of the
engine. Any engine in operation
subjects
its
Connecting rods should be checked for roundness and size. Typical tolerance
of .0003 ten thousandths per inch must be held.
various
rotating parts to severe inertia loads. If an engine is turnig 3500 RPM, consider that each piston and
rod assembly must stop, start in another direction, stop, restart in the opposite direction 7000 times
a minute or two times the RPM. It can be readily seen that if one assembly weighs more than the
others, the engine is going to shake in response to that inbalance. Most of us have experienced and
out-of-balance wheel on our automobile at sometime or another and have been made very aware
that an ounce or two out of balance can shake a ton or more of automobile to pieces if driven at that
23
particular speed.
In a four cylinder engine such as ours, with no counter balances on the crank, it is super important to make every effort possible to insure that the rotating mass is as nearly balanced as possible.
An out of balance engine wastes much of the energy it generates just simply vibrating instead of
smoothly delivering that energy to the prop where we can use it. Flying behind a smooth running
engine is certainly much more enjoyable, and a smooth engine will stay together much longer than
the unbalanced engine.
While balancing and the need for balancing is easy to understand, the tools and techniques
necessary will require that you send your parts to a shop specializing in that type of work.
Here is what the shop does for you as
they "balance" your engine. First, they
will remove the wrist pins from your
pistons and weigh the pistons to find the
lightest one, then machine the other three
to a weight equal to the light one. Weights
are equalized to a fraction of a gram. This
material is removed by machining on a
lathe. Next come the connecting rods
which is a two part operation, the big end
and the small end. As with the pistons,
rods are weighed on each end to find the
lightest rod. Weight is then removed by
careful grinding in certain areas on the
rod until all weights are equalized on each rod.
Now the crankshaft itself is balanced, but in a different manner. A good balancing shop will have
an electronic balancing machine that spins the crank and measures the amount of imbalance by
means of sensitive vibration pick-ups triggering strobe lights that tend to freeze the position of the
shaft, like a strobe timing light. The amount of imbalance is indicated on an electronic meter and
weight is removed by grinding or drilling on the heavy side until a smoothly rotating condition is
achieved.
On your engine, as you balance the crankshaft, you will balance the whole rotating assembly
which will consist of the propeller hub, crankshaft, and flywheel or the oil seal rear hub if your
engine is a simple one. Now many people are under the mistaken impression that because their
24
Rod weights are divided into two parts, the big end of
the rod and the small end. Each rod is brought to the
weight of the lightest one.
crank has balancing holes already drilled in it by the Volkswagen factory that it is not necessary to
rebalance. The shaft was factory balanced with a flywheel on it which you now have discarded or
replaced with a very light aircraft starter ring. The factory never did balance with the level of precision we are describing here.
The primary purpose of balancing is 1o equalize all of the rotating engine parts to ensure equal and stable inertia
25
Whether your engine is very simple or very complex, I believe that the balancing process is as
important to your engine's long life as having good oil in the crankcase. If there is no shop in your
locality that does balancing as described here, take the time and spend the money, usually about
$60.00, to send your engine out and have the work done. It's one of the best investments you can
make in your engine.
We can provide this service if you can't obtain it locally.
Ok, now that your basic parts are good, balanced, and ready for assembly, let's start putting the
lower end together. I am going to plague you with three more chapters before we get into the step
by step procedures, for there are a few more important things to consider.
NOTE: WHEN BALANCING THE CRANKSHAFT AND ITS ATTACHED PARTS, BE
SURE TO MARK THE FLYWHEEL AND CRANK SO THAT UPON FINAL ASSEMBLY THE
FLYWHEEL WILL BE PUT BACK ON THE CRANK IN THE SAME EXACT POSITION IT
WAS IN WHEN THE ASSEMBLY WAS BALANCED.
26
chapter 4
CRANKSHAFT ASSEMBLY
*This Chapter is included for information not found in the step by step. Read and understand both before assembly.
The major work and modification necessary to adapt a Volkswagen to aircraft is in the crankshaft
assembly. In addition to selecting the shaft (as in the preceeding chapter for the best suitability to
aircraft.) we must in some manner adapt a propeller hub to the former pulley end of the crank.
There are two generally accepted ways that have been used to do this. Both are mechanically sound
and should cause no problems. One method used is commonly called the "shrink fit" prop hub.
The advantage to this method is the crankshaft can remain standard on the pulley end. and no
machine is required. To install this type of prop hub. you first install the bearings, timing gear, and
oil slinger ring. The prop hub bore is an interference fit with the shaft. To install the hub on the
shaft we heat the hub to 350°, or slightly more, and get it on the shaft very quickly before the shaft
gets hot and swells too. When metal is heated it expands, and so the hole in the prop hub gets large
enough to slide over the shaft. I personally don't care for this type of hub because once installed
they are most difficult to remove without ruining your hub or shaft, or both due to the galling action
if you try to press the hub off the shaft later.
The tapered hub does require a matching taper be machined on your crankshaft, but is not difficult to disassemble with a gear puller. The job of machining the taper should be left to an expert
machinest, unless you have a good metal lathe and a dial indicator to set up the crank to run at no
more the .001 (thousandth) before you attempt to cut the taper. Even the job of cutting the taper,
which looks so simple on the blueprint, can turn into a can of worms very easily. Taper machining
must be extremely close or the tapers will not lock in full surface contact as they should. Your hub
will wobble and not have the ability to transmit power loads that it was designed to have. Whoever
furnishes you with a prop hub will probably, or at least should, furnish you with instructions on
how to install it. Just put it on exactly as the maker's instructions tell you to do, and then we will
proceed to put the rest of your crank together.
On the flywheel end of the crank you may install only an oil seal hub. such as is used on the KR-1
plans, or you may want to go the starter route and install the flywheel ring gear. Whatever you do at
this point you should have the crankshaft/ftywheel/prop hub assembly balanced as described in the
previous chapter.
27
When you receive your crankshaft assembly back from the balancer mark the positions of the
flywheel on the crank. Do so before disassembling the crank shaft assembly. Now, clean the crank
in solvent and be sure to flush all the oil passages with high pressure air. You have now had the
crank taper turned, and you have had it reground on the rods and mains and then balanced, so it may
well have picked up some crud somehwere along the way. So really clean it. This is the last time
before assembly.
Take the old flywheel that you saved and put it on your workbench in the metal drip pan.
You have got everything, bench, tools and parts spotlessly clean, right?
Stand the crank on the old flywheel so it's good and stable to work on. The first operation is to install the #3 bearing.* You should have the stud side of your crankcase either on the engine building
stand or on the bench where you can look at it for reference. Get your #3 bearing out of the bearing
set and check its placement in the case. You can first place the 4 dowel pins in their holes in the
bearing saddles, one in each bearing position. These dowels determine which way the bearing fits
on the shaft. You will notice that on the #3 bearing the dowel is toward the side of saddle away from
the prop. With this in mind, apply a coat of oil to the inside of the bearing and slip it onto the shaft
so that the dowel hole in the bearing is away from the prop.
Now check what you just did until you are completely sure that #3 main is positioned correctly,
because we are going to install the cam drive gear and distributor gear now, and if you are not right,
back you go to the shop for another arbor press disassembly.
Locate the two small dots on the front side of the cam drive gear. These will face foward towards
the prop. Be sure that the cam gear key fits in its slot. Place the cam drive gear on a hotplate, or
hold it in pliers over your own gas stove, or heat it with a propane torch to 350°F. This is not very
hot so don't go melting the thing, it is not necessary. By holding it with the pliers, it will slip very
easily over the shaft and its key into position. Let it cool there and let the shaft cool too as it will
soak the heat from the gear. Now, timing marks are on the front, right? Put on the spacer ring now,
heat and install the distributor gear in the same manner. When cool, install the snap ring in its
groove just ahead of the brass gear. Be very careful not to scratch #4 bearing surface while installing the snap ring. Also be careful that the ring does not snap off the snap ring pliers and get you in
the face. Maybe that is why they are called "snap rings". Now install the #4 bearing, and again
check and recheck the bearing to make sure you are insallting it the right way forward. There is a
groove on the inside diameter of the #4 that collects the excess oil and returns it to the sump. This
* The third bearing from the flywheel end.
28
help to identify the position of the bearing as the groove goes toward the propeller. From this point
to the propeller hub you are on your own. and must proceed with installing your prop hub in the
manner the hub maker has instructed. Of course if the hub is tapered, you would have machined
your crank already. But now you would proceed with the final assembly including slinger ring if required.
HAPI hubs are an exception here because we fit an oil seal behind the hub, and the hub must be
installed after the engine is assembled and hub seal is fitted to the case. The oil slinger ring is fitted
to the shaft at this time before the shaft assembly is fitted into the case.
chapter 5
"COOL IT"
When you rub two pieces of metal together, the more pressure there is and the faster you rub, the
more heat you will generate until ultimately the metal will melt or fuse together. If however, we can
put a film of oil between these two surfaces and keep it there, the heat can be minimized. To keep
the oil there, we have to have the room for it (tolerance) and pressure to keep that tolerance filled
with fresh oil.
Volkswagen engines are designed with excellent lubrication systems. They seldom have a bearing failure when the bearings are supplied with plenty of lubricating oil. The object is to get a tough
lubricating film of oil between the two rapidly moving pieces of metal. If the pieces of metal ever
actually come in contact, PRESTO! You've wiped out a bearing.
If we realize that most engine failures are due to lack of lubrication, then what are the causes of
lack of lubrication and what can we do about them? The biggest single cause of lubrication problems is HEAT! While it is true that oil breaks down with use, most bearing failures in air-cooled
engines are due to excess heat destroying its ability to lubricate. If an engine's oil temperature were
running at 200 °F and the oil temperature then climbed to 220 °F, the extra 20 °F has reduced the
ability to lubricate by 50%. Let the oil temp go to 240 °F and you loose another 50% o flubricating
power, so now you have only 25% of what you had at 200 °F. Very easy to see why you lose the
bearing quick at high temperatures.
We must control two things to insure the bearings will lubricate as they should. The bearings
must be installed with the correct tolerance or "oil space" to insure that our metal parts ride on the
oil film rather than touch. If set up too tight, there is no room for the oil film and the metal contacts
and burns. Too much space (tolerance), and we can't maintain the oil pressure to keep that film in
the bearing and it burns. Too tight or too loose, the result is the same, ruined bearings. To compound our problem, the air-cooled engine operates at much higher temperatures than the water
cooled, yet most oils are formulated for lower temp water cooled engines. We have found
that Valvoline 30 detergent works very well and is available all over the country. There are very
good oils formulated specifically for aircraft with air-cooled engines put out by Shell, Texaco,
Mobil, Standard Oil, and Gulf, to name only a few. They are higher in price than Valvoline and
viscosity index is a little more than Mosler likes, but they certainly will not harm your engine. Be
30
sure to get the 40 weight oil rather than the 50 weight or as some oil manufacturers market their
oils . . . 40 weight equals 80 grade, and 50 weight equals 100 grade . . . confusing isn't it? Just
get the lightest weight oil and you will be all right.
The oil in your crankcase won't do you any good if you don't have the pressure to constantly keep
feeding bearings. To do this you need a much larger volume and capacitv pump than stock. The
25mm by 8mm pump with a special heavy duty bypass valving setup will give you 50 PSI at idle and
70 to 80 at operating speeds, so you won't run out of pressure or volume at the bearing. Just having
pressure and volume isn't enough however. You also have to deliver COOL oil to the bearings.
perferably at a temperature well below the 220°F which should be considered the red line
"NEVER EXCEED" temperature.
The very term "aircooled" is somewhat misleading to some people. It tends to lead us into thinking that the air flowing over the cooling fins on the outside of the engine will disipate the heat
generated. This is not quite the case however. A great deal of the heat generated is absorbed by oil
in contact with these hot pans. In fact, oil can be a very effective cooling medium if we pass it
through a heat exchanger, or oil cooler as more commonly known. In passing the oil through this
cooler, which is exactly the same principle as the radiator on your car. we maintain its ability to
lubricate the engine effectively. Low oil level in the engine will decrease the cooler's effectiveness
just as low water level in your car will ultimately cause it to boil over. Low oil level will first result
in higher oil temperatures then possibly loss of oil pressure then loss of all the engine bearings.
We h a v e found the oil cooler on the Volkswagen conversion is as necessary as the magneto.
Don't believe anyone who tells you that you can fly a Volkswagen engine without it! You can get
away with high oil temps for a while but bearing life will be short. If Volkswagen engines would
run well without oil coolers, Volkswagen could have saved millions of dollars by not installing
them, but they did. on every Volkswagen sold. They also installed a blower to force cooling air
through a sheet metal ducting system to insure adequate flow of air through the cooling tins and oil
cooler.
In building your cowling you must be equally concerned and insure an adequate flow of air to
cool the engine properly. Too many builders will do an excellent job on their airframe and neglect
to give their engine the same careful attention to detail in the ducting and baffling of their clowings.
You must build baffling in such a manner that air coming into your cowl is directed through and
around the cylinder heads and cylinders. If you can. go to a local airport and look under the cowlings of as many light planes as possible. Try to make your baffling and cowling so tight a seal
around the engine that air can only pass through the engine in the areas where you want and not leak
^1
through without cooling. Your oil cooler must be placed where it can have a plentiful supply of air
flowing through it too! Notice I said "flowing through." Big intake areas don't mean a thing if the
air can't get out! In fact the general rule is two or more times the outlet area as the inlet area.
Remember that you are heating this air and thereby expanding it.
If this chapter scares you, it wasn't meant to, but, simply to point out how essential cooling is to
the air-cooled engine. Of course if you don't have a cylinder head temperature gauge and oil
temperature gauge you might not be aware of high temperatures until your engine has been ruined. I
strongly suggest that you plan on putting enough instruments in your bird to really monitor your
engines well-being. IT IS THE BEST ENGINE INSURANCE YOU CAN BUY! If you buy an
engine from a professional convenor, you still have to deal with the problems described in this
chapter. While most engine people will stand behind their engines to various extents, none of them
will be eager to repair or replace an engine because the buyer failed to install proper cooling
aparatus, and burned the engine up with overheating. No engine, regardless of who built it professional or amatuer, can survive long without proper cooling.
What it comes down to is this; First you cowl and duct it as well as you can. Then instrument, and
fly it to check and keep at it until you really "cool it." You will then have an engine that will serve
you faithully for hundreds of hours!
32
chapter 6
DISPLACEMENT,
COMPRESSION AND DECK HEIGHT
Anyone who has been around engines for some time has heard the term "Compression Ratio"
and should know that the higher the ratio the more power you get. But on the other hand, they do
not know exactly what the compression ratio is or why the higher the ratio the more power.
All internal combustion engines must compress the fuel/air mixture to receive a reasonable
amount of work from each power stroke. The air/fuel charge in the cylinder can be compared to a
coil spring in that the more you compress it, the more work it is potentially capable of doing.
The compression ratio of an engine is a comparison of the volume of space in a cylinder when the
piston is at the bottom of the stroke to the volume of space when the piston is at the top of the stroke.
This comparison is expressed as a ratio, hence the term "Compression Ratio." Compression ratio
is a controlling factor in maximum horsepower developed by an engine, but is limited by the grade
of fuel used, engine R.P.M., and operating manifold pressure. For example; if there is 534.85 Cu.
33
Cm. when the piston is at the bottom of the stroke and 76 41 Cu. Cm. when the piston is at the top
of the stroke, the compression would be 534.85 to 76.41.* If this ratio is expressed in fraction
form, it would be 534.85/76.41 or 7 to 1, usually represented as 7:1.
To grasp more thoroughly the limitation placed on compression ratios, manifold pressure and its
effect on compression pressures should be understood. Manifold pressure is the average absolute
pressure of the air or fuel/aircharge in the intake manifold, and is measured in units of inches of
mercury (Hg). Manifold pressure is dependent on engine speed (throttle setting) and super charging. The external exhaust driven Turbocharger is actually a centrifugal-driven air compressor. The
operation of which is to increase the weight of the air/fuel charge entering the cylinder. With the
use of a turbo you can have a manifold pressure considerably higher than the pressure of the outside
atmosphere.
The compression ratio and manifold pressure determine the pressure in the cylinder in that portion of the operating cycle when both valves are closed. The pressure of the charge before compression is determined by manifold pressure, while the pressure at the height of compression (just prior
to ignition) is determined by manifold pressure times the compression ratio. For example; if an
engine were operating at a manifold pressure of 30" Hg. with a compression ratio of 7:1, the
pressure at the instant before ignition would be approximately 210" Hg. However, at a manifold
pressure of 4 5 " Hg. the pressure would be 315" Hg.
Without going into great detail, it has been shown that the compression event magnifies the effect
of varying the manifold pressure, and the magnitude of both effects the pressure of the fuel charge
just before the instant of ignition. If the pressure at this time becomes too high, premature ignition
or knock will occur and produce overheating.
One of the reasons for using a higher compression ratio is to obtain long-range fuel economy.
That is, to convert more heat energy into useful power than is done in engines with a low compression ratio.
Here again, a compromise is needed between the demand for fuel economy and the demand for
maximum horsepower without knocking.
Many people before us have experimented with different compression ratios on V.W.'s and have
come up with a range in which you get best power and reliability. Most agree that a turbo charged
engine should be 7.5 to one or less, and the normally aspirated engine 8.5 to 1 to 9.0 to 1. So, once
you have decided what compression ratio you are going to use, you must set this up when building
* Figures used represent 1835 C. C. V. W. Engines.
34
your engine. The way we have control over the compression ratio is with the deck height and size of
the combustion chamber in the head, which together control the total size of the compression ratio.
The larger the chamber, the lower the compression ratio, the smaller, the higher the ratio. The size
of the combustion chamber in the head will be determined by the macine shop that C.C.'s your
heads, making all the combustion chambers the same size. If the machine shop does a lot of this
kind of work, they may be able to tell you what deck height you need to get the desired compression
ratio. If not, it is not difficult to figure it out yourself. All you need to know from the machine shop
is the size of the head combustion chamber in C.C.'s (cubic centimeters).
At the point of assembling your engine, your only control over the compression ratio is with the
"deck height," which is the space between the top of the piston and the top of the cylinder with the
piston at the top of the stroke (measure parallel to piston pin).
We have discussed how to find what compression ratio you already have. Now we will find out
how to build an engine with the compression ratio you want.
Refering to the picture on page 33 (compression ratio 7:1) you will see the total volume is made
up of 7 equal parts, 6 equal parts in the displacement volume, and one equal part in the clearance
volume (The displacement volume is determined by the bore size and the stroke of the engine. The
clearnace volume is determined by the size of the combustion chamber in the head and the volume
of space in the deck height). For example, a compression ratio of 8.5 to 1 the total volume would
have 8.5 equal parts, 7.5 of which would be displacement volume, 1 of which would be clearance
volume. Note: The number of equal parts in the displacement volume is equal to compression ratio
minus 1. Also note that the clearance volume is equal to one part.
The following procedure can be used on any size engine . Just change the numbers to fit your
engine. Example: You are building an 1835 C.C. engine with a compression ratio of 8.5 to 1:
92mm Bore
69mm Stroke
10mm = 1 cm.
50 C.C. In Heads Combustion Chamber
The displacement volume = pi R2H
pi
= 3.14
R = 1/2 bore or 46mm or 4.6cm
H = Stroke or 69mm or 6.9cm
Displacement Volume in C.C.'s = 3.14 x 4.6cm x 4.6cm x 6.9cm = 458.45cc
35
Compression ratio minus one equals number of equal parts in displacement volume.
8 . 5 - 1 = 7.5
Displacement volume divided by number of equal parts equals size of one part.
458.45cc = 61.13cc
7.5
Clearance volume is equal to one part or 61.13cc clearance volume minus heads combustion
chamber size equals volume of space in deck height,
61.13cc-50cc - 11.13cc
We need 11.13 of volume in our deck height to have a compression ratio of 8.5 to 1. To find out
how many cc in .001".
1" = 2.54cm
.001" = .00254cm
Volume = pi R2H = 3.14 x 4.6cm x 4.6cm x .00254cm = .169cm
.001" in Deck Height = .169cc
11.13cc = 66 or .066" Deck Height
.169cc
For an engine with a stroke of 69mm, bore of 92mm, head size of 50cc, you need .066" of deck
height ot have a compression ratio of 8.5 to 1.
Minimum deck height allowable is .055 (thousandths). Any less would allow pistons to hit heads
at high speed due to metal stretch. We try to set everything up to get about .080" deck height.
36
chapter 7
VOLKSWAGEN ENGINE
IDENTITY NUMBERING SYSTEM
Volkswagen over the years has built many engine variations both in the basic engine displacement, and in variations of the same displacement engine for different applications.
Volkswagen type numbers and descriptions:
Type I - Sedan (Bug) Super Beetle, Ghia and The Thing
Type II - Transporter, Camper, Kombi, Station Wagon and Commercials
8 Models
16 Models
Type III - Fastback, Squareback and Variant
3 Models
Type IV - 2 Door, 4 Door Sedans and Station Wagons
3 Models
On the Type I and Type II, engine numbers are found stamped on the crankcase under the
generator supports facing the rear of the car or pulley end of the engine.
Type III engines are all 1500 or 1600 C.C. and underneath the tin are the same crankcases as used
in Type I and Type II with very minor mechanical changes in casting. These Type III engines are
usually easier to obtain and make an excellent core engine to start with. Many of the 1600 C.C.
Type III engines have dual port heads and are equipped with fuel injection. The fuel injection is
useless to us, but the basic dual port engine is the one for you if you want to Turbo your engine. The
engine number on Type III is found on the rear (opposite flywheel) end of the engine between the
oil cooler bracket and the crankcase split line. This area is usually covered with grease and crud on
the used engine. So if it's a pancake engine and not a Type IV pancake, it is suitable for conversion.
Type IV. This engine is 1700 C.C. or more and was first marketed here in 1970. It is an entirely
different engine from the others described here and is totally UNSUITABLE for conversion as
described in this book. See page 73 note " B " .
All of the engines listed here can be converted by methods described. However, the underlined
engines are the most desirable for conversion.
The following listing includes only the year, models, and engine numbers that are usable for conversions as described in this book:
37
TYPE I ENGINES
First Built
8 - 1966
8 - 1969
1971
8 - 1971
July 1972
August 1972
July 1973
AE changed to -
Engine Numbers
H-0-000-000
B-0-000-000
AD-0-360-022
AE-0-000-001
AD0-360-025
AE-O-558-001
AH-0-000-000
See
AD-O-058-001 Note A
AE-0-017-063
AH 0 006 900 Page 73
AD-0-598-002
AE-0-917-264
AF-0-000-802
AH-0-005-901
AD-0-749-788
AK-0-060-039
AF-0-034-850
AH-0-056-934
1500 C.C
1600 C.C
50 H.P.
1600
1600
1600
1600
1600
1600
1600
1600
1600
1600
1600
1600
1600
1600
1600
50
48
48
48
48
48
48
50
48
46
48
50
48
46
48
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
C.C
HP.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
Super Beetle
(Smog Control)
(Smog Control
(Smog Con rol)
T Y P E II E N G I N E S
Dec. 1963
Aug. 1964
Oct. 1964
Dec. 1964
Aug. 1965
Aug. 1966
Dec. 1966
July 1967
Aug. 1967
Dec. 1967
July 1968
Aug. 1968
Dec. 1968
July 1969
Aug. 1969
Dec. 1969
July 1970
Aug. 1970
July 1971
8-264-628
8-785-398
8-964-971
816-281
H-0-000-000
L-0-000-000
H-0-183-373
H-0-309-830
H-0-761-325
B-5-000-001
B-5-017-633
C-0-000-000
B-5-050-173
B-5-050-174
B-5-079-928
B-5-116-436
B-5-116-437
B-5-114-597
B-5-230-000
AE-0-000-001
AE-0-529-815
1500 C.C.
1500 C.C.
15O0 C.C.
1500 C.C.
1500 C.C.
1500 C.C. (Smog Control)
1500 C.C. 12 Volt System
1600 C.C. Engine Started
1600 C.C.
1600 C.C. Has M340 Smog Control
1600 C.C.
1600 C.C.
1600 C.C.
1600 C.C.
1600 C.C.
1600 C.C.
1600 C.C.
1600 C.C.
1600 C.C. Last 1600 C.C. Bus Engine
TYPE III ENGINES
April 1961
Dec. 1961
Aug. 1962
1500 C.C.
1500 C.C.
1500 C.C.
000- 001
013-112
065-746
38
Dec. 1962
Aug. 1963
Dec. 1963
July 1964
Aug. 1964
Dec. 1964
July 1965
Aug. 1965
Aug. 1966
Aug. 1967
thru
Dec. 1972
T0-000U0-0000
143-557
255-340
408-183
633-330
633-331
816-281
1-100-000
001
T-0-160-001
000
1500 C.C.
1500 C.C.
1500 C.C
1500 C.C.
1500 C.C.
1500 C.C.
1500 C.C.
1600 C.C. Started
1600 C.C. 12 volt
1600 C.C. Fuel injection started
U0-069-142
1600 C.C. Note: all " U " series engines
are dual port.
Though any of the 1500 - 1600 C.C. engines on the previous page will convert to aircraft, the
most desirable engines are the later cases as used in the transporter. These have dual oil relief
valves, (about 1970 and on), and bosses on the case for the rear engine mount as used in the bus.
These cases were used in the Type II and the Type III vehicles.
1500 - 1600 STANDARD CRANKSHAFT BEARING JOURNAL SIZE
Bearing 1, 2, 3 2.1640" - 2.1648"
Bearing 4 1.5739" - 1.5748"
ROD JOURNAL SIZE
2.1644" -2.1653"
1500 - 1600 STANDARD CAM SHAFT CAM BEARING JOURNALS
Bearing 1, 2, 3 .9837" -9842"
39
"How To Build A Reliable VW Aero Engine"
is available on VHS video tape from:
Viking Aircraft, Inc.
P.O. Box 646
Elkhorn,WI 53121
Phone 414-723-1048
Fax 414 723 1049
chapter 8
BUILDING IT, STEP BY STEP
So now we are ready to start putting your engine together. Work bench is CLEAN, tools are
CLEAN, and your parts are CLEAN, right?
STEP 1
We will start by setting the crankshaft upright in your clean metal tray, and assembling
the front end. There is some other preparatory to be done at this stage.
STEP 2
(SEE FIGURE 1) Put all the dowels in the cases (SEE FIGURE 19) on the stud side of
the case, one in each bearing and one in the center main on the female side of the case.
Now take the #1,3,4 bearings, they are the full circle bearings, and place them in the
case over their dowel pins and gently push them into proper position. Now lightly
scribe a mark on each side of the bearings as shown in FIGURE 1. When we insert the
shaft in the case these marks will help you in aligning the bearings in proper position.
STEP 3
Liberally coat the inside of #3 bearing and place it on your shaft with the dowel hole
toward the flywheel end as shown in FIGURE #4, 5, 6, 7. Make double sure it's
oriented properly.
STEP 4
(SEE FIGURE 2, 3) Prepare to install the cam driver gear by identifying the timing
mark side. This gear has a 45° bevel on the side toward the flywheel and 2 marks as
shown in figure 2 on the propeller side. It sits on the shaft over a large key. To install,
heat to 350 °F. with a torch, or in your wife's oven, or on a hotplate. This will cause the
gear to expand. By grasping it with pliers as shown in FIGURE 4, you will be able to
place it over the shaft and into position with no trouble. Let it cool before beginning the
next step!
40
FIGURE 1
FIGURE 4
FIGURE 5
FIGURE 2
FIGURE 3
FIGURE 7
41
STEP ;>
(SEE FIGURE 4) Place spacer ring on shaft between cam driver gear and distributor
driver gear as shown in FIGURE #6. and 7.
STEP 6
(SEE FIGURE 5. 6. 7) Install the distributor driver gear on the shaft by heating in the
same manner as the cam driver gear.
STEP 7
(SEE FIGURE 8. 9) Using snap ring pliers install the snap ring in its groove ahead of
the distributor driver gear. Be sure it is completely seated and in the groove. Be careful
of your face and eyes when installing this "snap ring." They usually snap off at least
twice during this operation.
STEP 8
(SEE FIGURE 10) Installing connecting rods. The very first thing is to get the
crankshaft and rods properly oriented so the rod offset will be correct when assembled.
This is SUPER important. Many Volkswagen wrist pin failures can be traced to improper connecting rod installation. With the flywheel end of the shaft toward you. and
the shaft laying down on the bench pointing away, turn the crank so the rearmost (near
flywheel) rod throw is on your right side (SEE FIGURE 13). The connecting rods are
marked with a forge mark on one side as shown in FIGURE 12. These forge marks
must be up. or toward the top of the engine, when assembled or rod offset wilt be incorrect. (SEE FIGURE #27 for proper relationship).
NOTE: We have not included instructions for valve grinding or reseating, since this requires specialized fooling and experience. Catalog lists all valve train parts normally used in H.A. P. I. engines. We encourage you to let an expert build
or rebuild your heads.
STEP 9
(SEE FIGURE 11) Take the rod cap off the first rod. Even here you can ruin your rods.
To remove the caps, clamp the big end in >our vice between 2 pieces of wood and
remove the nuts. Note the notches to retain bearing tabs on both rod and cap.
STEP 10
(SEE FIGURE 12) Install bearing halves in both rod and cap. slipping them into place
with gentle finger pressure. To avoid the possibility of mixing rods or caps do only one
at a time. Install the rod on the shaft in proper position (SEE FIGURE 27) being sure
that cap is oriented properly. The cap has numbers stamped on one side only to match
numbers on rod one side only. Stamped numbers must be on the same side. Install the
rods only snug tight now, we will torque them later when all are in position. Be sure to
coat the journal and bearing with oil when assembling. (See note page 40 , step 3)
STEP 11
With all 4 rods in position and forge marks in proper position, rod caps on correctly,
bearings lubricated, we can now start tightenins. Set your torque wrench to 8 Ft. Lbs.
FIGURE 8
FIGURE 9
FIGURE 11
FIGURE 12
FIGURE 14
FIGURE 15
FIGURE 13
FIGURE 16
FIGURE 10
43
torque and tighten all rod bolts to that figure. Reset your torque wrench to 20 Ft. Lbs.
and go over the nuts again. Now take a large rubber hammer or rawhide mallet and
firmly hit each rod cap firmly on the side over the bolt area. This is to make the rod cap
align itself perfectly. If you don't have a rubber or rawhide hammer, place a block of
clean wood over the rod and hit the wood with a hard hammer. Now. with a feeler
gauge check the side clearance of the rods on the shaft. They must be not less than .004
and not more than .015 clearance. If clearance is correct now give your rods a final torquing to 23 Ft. Lbs. as shown in FIGURE 15. If the rod bearings are properly fitted
they will be free, but a little on the snug side. An easy test for proper fit is to lift up the
wrist pin end of the rod with the shaft in a horizontal position and let it fall. It should
fall slowly but steadily with noticeable but not excessive drag.
STEP 12
Using a center punch, deform the lock-lip downward into the slot to safety the rod
bolts. Do all eight bolts and recheck them. Some rod bolt manufacturers state this is not
necessary, but this guarantees that your rod nuts stay on. (SEE FIGURE 17).
STEP 13
At this point your crank should look like Figure 27 and have all its forge marks and
crank throws exactly as pictured. Check it carefully.
STEP 14
Now you are ready to prepare your case to receive the shaft. All five dowels should be
in place (SEE FIGURE 19) and you can now install the til bearing halves in each side
of the case. (SEE FIGURE 20) Refer to Step 2.
STEP 15
Place the cam followers in place, 4 in each case. Oil them, then push them in the case.
If they seem to be tight, work them up and down a few times to free them. Make 2 simple little wire retainers from a coat hanger wire as per sketch (see page 74 ) to hold the
lifters in the upper side of the case when you are assembling. FIGURE 21 & 22.
STEP 16
Install the camshaft bearings now. The order in which bearings are installed is very important. Separate the bearing shells first by width. The narrowest bearing goes at the
flywheel end of the cam. The widest set of bearings go next to the cam gear. Now, this
bearing is unusual in that it is designed to compensate for cam thrust. You will note that
one half of this bearing is flanged and the other half is flat like the other 2 bearings. The
flanged side of the bearing goes next to the cam gear on the stud side of the case. The
flanged bearing is shown in FIGURE 23.
STEP 17
Go back and recheck the bearing dowel pin hole in #3 bearing. Check that cam gear
timing marks are on prop side, snap ring is in place as shown in FIGURE 24.
44
FIGURE 23
FIGURE 21
tm 1111 n n r
FIGURE 18
FIGURE 24
FIGURE 19
FIGURE 22
FIGURE 25
45
STEP 18
Modify your oil slinger ring by cutting 3 tabs in it at 120° apart. 1/4 inch wide, by
hacksawing 1/4 inch into the slinger as shown in FIGURE 25. After debuning, bend the
tabs created forward 1/8 inch.
STEP 19
Oil the inside of the #4 main bearing and place it on the crankshaft as shown in
FIGURE 26. This bearing has a groove on the inside of the bearing that goes toward
the prop. On the outside of the bearing is a machined round groove that has one side
open to the bearing edge. This faces the flywheel.
STEP 20
Place oil slinger ring on shaft as shown in FIGURE 26 with cupped side toward prop.
STEP 21
Now again, inspect the crankshaft assembly. Make sure the rods and forge marks are
oriented as shown in FIGURE 27. Check all the rod nuts and make sure they are salety
punched.
STEP 22
Now we will place the crankshaft in the crankcase. Put the rear main bearing on it. be
sure to oil it first, and make sure that dowel hole is toward the flywheel end of the
crankshaft.
STEP 23
Your crankcase stud side is rotated in its stand or placed on the bench with the studs
pointing straight up. Carefully consider which rod goes into which cylinder. The rearmost rod towards the flywheel and the next to front rod go through the holes in this side
of the case. Grab the shaft and support it by holding it in mid-air by the two rods that go
into the female side of the case. Now gently lower the crank assembly into the case until it rests there. Now you will have to turn all the bearings so the scribe marks you
made are on the case split line. Usually the #4 and #3 bearings will have to be moved
either forward or back to get them on their dowels. Number 3 usually must be positioned properly before the dowel in #4 can seat. Turn the #1 bearing until the scribe marks
line up and it should tend to move into place. Go very slowly with gentle pressures, no
force, just keep moving it until everything lines up and it will go into place. If you
marked the bearings correctly the scribe lines will be on the case split line when crank
is seated. A great many bearings have been damaged or destroyed by impatient
mechanics right here because they used force in an effort to get the shaft assembly
seated. When everything is in proper position, it will go into position easily.
STEP 24
The camshaft is now installed in the crankcase. Be sure that the one timing mark on one
tooth on the prop side of the cam gear is placed between the 2 marked teeth on the cam
driver gear or your cam timing will be incorrect. (SEE FIGURE 30).
46
FIGURE 30
FIGURE 26
FIGURE 31
FIGURE 27
FIGURE 28
FIGURE 3 2
FIGURE 33
FIGURE 29
STEP 25
You must now make sure that your camshaft gear and the cam driver gear have
backlash. The book says .000 - .002 but we like to see at least .001 between the teeth.
This is very difficult for the non-professional to check so we simply slide the crankshaft
back and forth in its bearings. The cam gear should have enough clearance to allow this
sliding without binding. If not, you may have to get a smaller cam driver gear (big
gear) but this doesn't happen often. See Note " C " page
STEP 26 Liberally coal the toe of the cam lobes and face of thevalve lifters with grease (supplied with HAPI cams). This is to insure the cam and lifter do not score on the initial
start-up.
STEP 27
Place cam plug in stud side of the case sealing it with aircraft "Permatex" to avoid an
oil leak at this point. (SEE FIGURE 31).
STEP 28
Now install six " 0 " rings, one on each of the studs. These " O " rings keep the oil inside the case, so don't forget them.
STEP 29
(OPTIONAL) If you are installing a windage tray in your engine to keep down oil
frothing insert it into position. It's placed just below the crankshaft on the stud side of
the case at this point. (NOT ILLUSTRATED).
STEP 30
Your case should now look like FIGURE 33 and is ready to be mated with the other
side. Double check everything you have done at this point and be sure there are no
mistakes, nothing omitted.
STEP 31
Prepare the case for mating by putting a very light coat of aircraft Permatex on the sealing surfaces. Don't get carried away and slop alot of this goop on, it isn't necessary and
just makes a mess of things. Just a real thin coat all the way around the seal area is all
that's needed.
STEP 32
Ok, now pick up the female side of the case and gently slide it down the studs to mate
with the stud side. If you have gotten everything lined up properly, the cases should
close with very light pressure. You may tap them VERY LIGHTLY with a soft hammer to close the case. Be sure that the case closes evenly all the way around. Case
should close to the thickness of a paper matchbook cover very easily. If they won't,
you have something out of place, so take them apart and find the offending part and
position it properly. Usually, it's one of the main bearings not down on its dowel pin
properly. Refer to FIGURE 36. That's the way the case should be closed before you
48
FIGURE 37
FIGURE 34
FIGURE 38
FIGURE 35
FIGURE 39
FIGURE 36
49
FIGURE 40
even start to put nuts on it and tighten anything. Just take your time and don't get annoyed, it will almost fall together when properly aligned.
STEP 33
Place the 6 flat washers over the 6 thru studs and finger tighten the nuts only. Now go
around the case and put the 8mm nuts on the stud using a wavey washer under each
one. (SEE FIGURE 37).
STEP 34
Using your torque wrench, tighten the nut shown in figure 38 to 7 Ft. Lbs. torque first.
Now go to the thru studs and tighten the center ones first to 10 Ft. Lbs., then the end
ones. Now go around the case and tighten all the 8mm nuts to 10 Ft. Lbs. Now reset
your torque wrench to 14 Ft. Lbs. and retighten the 6 big nuts. Change sockets and
tighten all the small nuts to 14 Ft. Lbs. Now change sockets again, and set torque
wrench for 20 Ft. Lbs. and tighten all big nuts. Reset torque wrench to 25 Ft. Lbs. and
final tighten big nuts. Reset torque wrench to 14 Ft. Lbs. and recheck small nuts. Now
comes the moment of truth. If you did everything right, your crankshaft will turn using
only your bare hands, it should turn with some drag, but not too much. It will resist
starting to move but move easily once it starts moving. If your crank turns, "you've
done good, boy" if not "you're in a heap of trouble."
STEP 35
If you've received your pistons and cylinders from HAPI this step will be done for
you. If not we will now install the pistons in the cylinders. First put the piston rings on
the pistons as per the manufacturer's instructions that came with your rings. Referring
to FIGURE 40 we liberally oil the rings. We then place piston ring gaps at 120°
equadistant intervals around the piston. (SEE FIGURE 41). Now look closely at the
top of your piston. You will find an arrow stamped on the top of the piston. This arrow
must point toward the flywheel. Why? Volkswagen pistons have the wristpins placed
off center in the pistons, and if you get the piston in backwards the offset is in the
wrong direction. You will find this arrow on all four pistons.
STEP 36
Figure out which side of the cylinder is going to be toward the rear and compress the
rings with a ring compressor then push the piston by hand pressure only into the bottom
of the cylinder. (SEE FIGURE 43). When the piston is in the cylinder past the ring
lands, but with the wrist pin still exposed, you are ready to install it on the rod.
STEP 37
We are now going to install the pistons and cylinders, but temporarily, so don't put any
Permatex or any gaskets under them. Our whole purpose with this temporary operation
is to find out what "Deck Height" we have.
50
FIGURE 41
FIGURE 44
FIGURE 42
FIGURE 45
FIGURE 43
51
STEP 38
Refer to FIGURE 53 and install the wrist pins in the rods by pushing them in place by
hand pressure ONLY. After you have the piston and cylinder installed check to see that
the flat side of the cylinder is toward the other cylinder and make sure that little arrow
on the piston top points at the flywheel end of the engine. Many wrist pin failures in
V.W. engines can be directly traced to failure to get the pistons or rods or both in the
proper directions. It is not necessary or advisable to have the cylinder studs in now,
they will just be in your way.
STEP 39
Refer to FIGURE 45. Bring the piston to exact top dead center and then, using a wide
base depth micrometer, measure the distance from the top of the cylinder to the top of
the piston. You must measure at the center of the piston with your micrometer parallel
to the wrist pin. Be very sure that the cylinder is seated at its base against the case.
STEP 40
Mark the box your piston and cylinder assemblies came in as shown in FIGURE 46.
LF. for left front cylinder, LR. for left rear and so on. Gop through all the cylinders
with this step and return the piston and cylinder to the box as you finish each assembly,
writing on the lid the measurement for that cylinder. As you can see from the illustration there is some variation between cylinders, but usually very little variation from
cylinder to cylinder on the same side of the engine. Most variation is between one side
and the other. This is normal due to slight variation in cases and allowable machine
tolerances. Our objective here is to know where we are so we can set the deck height
properly. This is one of the most important adjustments on the engine, SO DO IT
RIGHT! In FIGURE 46 you will note we have .056 on the left side and .061 on the
right side. At
HAPI
we C.C. the heads and machine them so that the proper combus-
tion chamber volume is obtained for 8.5 to 1 compression ratio when deck height is set
at .080 thousandths. In this case we need .024 on the left side, and .019 on the right, to
add up to the desired .080 thousandths. To get these numbers we use "barrel shims"
under the base of the cylinder. These come in various thicknesses and the right shim or
combination of shims is now selected for each cylinder to add up to the correct deck
height. It's not that easy however, as a .020 shim never measures .020 due to the
tolerances in thickness on the material it's stamped from. This is going to be a stumbling block for you homebuilders. We have a large assortment of shims in various
thicknesses and measure them with a micrometer to find the exact size combination for
each cylinder. It is essential that the cylinders on the same side of the engine have the
shims adjust the deck height the exact same dimension on both cylinders. There can be
52
FIGURE 46
FIGURE 47
FIGURE 49
FIGURE 50
FIGURE 48
FIGURE 51
FIGURE 52
FIGURE 53
53
a slight difference of no more than .005 from one side of the engine to the other. See
note " D " page 73 .
STEP 41
We now install the cylinder hold-down studs in the engine. There are a total of 16
studs, 9 long ones and 7 short ones. The long ones go on the bottom side of the engine
and the short ones go on the top side. One long goes on the top right side in the last hole
nearest the flywheel. Place 2 nuts on each stud (SEE FIGURE 48) as you install it. Permatex the threads and install them snuggly into the case with 10 Ft. Lbs. torque.
Remove the jam nuts and go to the next one until all are installed.
STEP 42
We now are about ready to finally install the piston and cylinder assemblies. You have
by now matched the proper thickness barrel spacers to each of your piston and cylinder
assemblies and everything adds up to .080, right? Put a light coat of Silcone seal (See
note " E " page 73 ) on both sides of the barrel shim or shims under each barrel and install the shims on the barrels now. Don't mix up the shims or the barrels. (SEE
FIGURE 49 and 50)
STEP 43
Put a wrist pin keeper (See note " F " ) in the piston side that faces the other barrel, or
the flat side of the barrel. This allows you to install wrist pins from the open side. Install keeper as shown in FIGURE 51.
STEP 44
Liberally oil the wrist pin bushing. (SEE FIGURE 52 BEFORE INSTALLING
PISTON CYLINDER ASSEMBLY)
STEP 45
Place piston cylinder assembly over cylinder studs. Be sure your shims are on it, and
line up rod with wrist pin, then push the pin home with your thumbs as shown in
FIGURE 53.
STEP 46
VERY IMPORTANT! Before you even attempt to place the wrist pin keeper in the
piston, plug up the sides of the case with clean shop towels as shown in FIGURE 54.
The clips often jump off the pliers and if they can, always go inside the engine. Then
many times you can't get them out and you have to split the case to get the clip. Put the
towels in place so the clip can't fall in the case. Now put the clip in place. Push the
cylinder down to seat it and repeat the procedure until all cylinders are installed.
STEP 47
Check all the arrows on your piston tops, they all point to the flywheel, right? All your
pistons have wrist pin clips on each end of the pin, right? An easy way to keep count is
to lay out all 8 clips before you start and make sure you use them.
54
FIGURE 54
FIGURE 5 8
FIGURE 55
FIGURE 59
FIGURE 6 0
FIGURE 56
FIGURE 61
FIGURE 57
55
STEP 48
If this engine is to be pressure cowled, you now install the lower cylinder shrouds as
shown in FIGURE 56. They are designed to snap onto the cylinder hold down studs but
have to have some trimming done on the inside with tin snip to clear the increased size
of the big 92mm barrels. Trim about 1/8 inch off the turned down edges and they will
fit well.
STEP 49
Now coat the beveled edges of the push rod tube receiver holes in the head as per
FIGURE 57 and also the holes in the case where the other end of the tubes go.
STEP 50
Now place the beveled " O " rings on the push rod tubes. (Always use new ones) No
Permatex required here as shown in FIGURE 59.
STEP 51
Look at the bottom of your heads in the area indicated by " X " in FIGURE 60. These
should be spotlessly clean, and the surface in contact with the top lip of the cylinders
should be free of any marks or defects that could cause a leak and loss of compression.
V.W. uses no head gasket and depends entirely on a metal-to-metal contact to seal head
pressures.
STEP 52
Now turn your stand so that the cylinders are vertical and put the head on that side, but
don't push it all the way down yet. (SEE FIGURE 61)
STEP 53
Set 4 pushrod tubes in position as per FIGURE 62. Now bring the head down and push
one end of it down a little farther than the other, then start aligning the pushrod tubes
into their proper holes as you seat the head. No force now, just easy pressure. Be sure
everything is lined up, and that you don't bend the ends on the pushrod tubes.
STEP 54
SEE FIGURE 65 for the tightening sequence for the head bolts. Note that in the upper
illustration the numerical reference is different from the lower illustration. It is very
important that the proper sequence and torque be used or damage to the cylinder hold
down studs or case could result.
STEP 55
After putting a flat washer on each pad, run the nuts on finger tight and adjust your torque wrench to 7 Ft. Lbs. Tighten the head to this figure using the " A " sequence (SEE
FIGURE 66).
STEP 56
Rotate your engine on its stand and repeat the procedure up through step 55 on the opposite side of the engine. Also torque that side up to 7 Ft. Lbs. only.
STEP 57
Now, reset your torque wrench to 12 Ft. Lbs. and retorque all the head bolts using the
" B " sequence in FIGURE 65. When you have reached this figure on all the head bolts,
56
FIGURE 66
FIGURE 62
FIGURE 63
FIGURE 67
FIGURE 68
FIGURE 64
SEQUENCE #1
Torque to 7ft. lbs.
SEQUENCE #2
Torque to 18 ft. lbs.
Sequence #3 torque to 22 ft. lbs,
FIGURE 65
57
FIGURE 69
reset the torque wrench to 18 Ft. Lbs. if your engine has 8mm head studs, or set it at 23
Ft. Lbs. if you have the 10mm stud, as used in some of the older engines. Finally
tighten all the head bolts by the "B" sequence and your heads are now officially "on".
STEP 58
Place one of the small rubber " O " rings over each of the rocker shaft hold down bolts
as illustrated in FIGURE 67.
STEP 59
Now, we are ready to install the pushrods. First we better check them for straightness.
We do that the way the neighborhood shark picks a cue stick. Roll each one of them on
a flat surface. If they are bent it will be obvious when rolled.
STEP 60
Now that we have eight straight pushrods, blow through each one of them to clear out
any crud that may be hiding inside the tube. Drop one down each pushrod tube, which
end down doesn't matter, they're symmtrical. Put a little oil, on each one when installing it as shown in FIGURE 68.
STEP 61
Put a little oil on the exposed end of the pushrod to make them ready for installation of
the rocker arm shaft.
STEP 62
Now put a little dab of Permatex on the pad around each " O " ring as shown in
FIGURE 70. Also give the stem end of each valve a little gob of the cam lube grease to
prelubricate them a little bit. Squirt a little oil on the valve stem too, it's good for them.
(SEE FIGURE 71)
STEP 63
Place the rocker shaft and arm assembly in place and install one wavy washer SEE
FIGURE 72 on each stud before hand tightening the nuts. Be sure that each pushrod is
seated in the little cup on the pushrod end of the rocker arm.
STEP 64
Now run down the rocker stud nuts only about 3 turns, do not attempt to tighten them
yet.
STEP 65
Loosen the lock nuts on each of the tappet adjustment screws, and back the screw out 4
turns minimum. (SEE FIGURE 74)
STEP 66
Now go back and tighten the rocker arm shaft hold-down bolts to a torque setting of 18
Ft. Lbs. Be sure to pull them down evenly.
STEP 67
Repeat the same procedures on the other head to bring it up through step 66.
STEP 68
The Volkswagen oil pump and oil pressure relief and control valves are inadequate for
aircraft service. We will replace the oil control system with a high pressure by-pass
58
FIGURE 74
FIGURE 70
FIGURE 75
FIGURE 76
FIGURE 72
FIGURE 77
FIGURE 73
FIGURE 78
59
valve system as illustrated in FIGURE 75. Note the differences in the pistons and the
lengths of the springs.
STEP 69
Place the plain piston, the one without the groove aound it, into the hole at the flywheel
end of the engine. It goes in head end first, then the short spring is placed in behind it,
as shown in FIGURES 76, 77 and 78. Now place the plug and washer and tighten them
to 10 Ft. Lbs.
STEP 70
Now put the prop end oil control valve in head end first as shown in FIGURE 79. Place
the long spring behind it and secure in place with the plug as illustrated in FIGURE 81.
Tighten plug to 10 Ft. Lbs.
STEP 71
If working with a new case it will be necessary to install 8mm studs into the case to retain the oil pump. We use "Locktite" stud and bearing mount thread locking compound on the on-threads as we place them in their holes. Use the double nut system,
(same as the head studs) to tighten them in place. (SEE FIGURE 82)
STEP 72
Paint a thin coat of Permatex on the back side of the mounting flange only as per
FIGURE 83.
STEP 73
Find the proper gasket in your set and put it on the pump housing as shown in FIGURE
84.
STEP 74
Put the oil pump housing, with gears removed, on the four studs. Make sure the
through hole for the upper gear is in line to mate with the camshaft. (SEE FIGURE 85)
With a block of wood and rubber hammer, gently tap it into place on the case. (SEE
FIGURE 86) It will be snug but not excessively tight. Just be very sure that as you tap it
into place you keep it square with the case, and going in evenly.
STEP 75
Now place the gears in the pump as shown in FIGURE 87. The lower gear has the hole
through it and is the idler gear, while the upper gear has a long shaft that goes through
the pump housing and engages the driver slot in the camshaft.
STEP 76
Put the gasket (a thin paper one) on the front of the pump with a tiny bit of Permatex.
Many times the gasket sets will have gaskets made for the 6mm studs instead of the
8mm as we use. In that case you trim the ears off the gasket as shown in FIGURE 87
and this will allow you to use it. Now place cover on it.
STEP 77
Place 4 wavy washers, one on each oil pump stud, then 4 nuts. Torque them to 14 Ft.
Lbs.
60
FIGURE 86
FIGURE 79
FIGURE 82
FIGURE 87
FIGURE 83
FIGURE 80
FIGURE 88
FIGURE 84
FIGURE 89
FIGURE 85
FIGURE 81
61
STEP 78 The V. W. engine has an oil strainer system built in which is capable of keeping the big
lumps out of the oil passages, but that's about all. To install it you first place one of the
paper gaskets over the 6mm studs on the bottom of the case. Permatex both sides as
you do. Next place the strainer in, as shown in FIGURE 88, then put another gasket,
Permatexed on both sides on the top of the strainer.
STEP 79
Put the oil sump cover on over the six studs. Now look in your gasket set and find 6 little copper washers there. Place on of these on each stud and secure the sump plate with
6 acorn nuts as shown in FIGURE 89. Torque the nuts to 6 Ft. Lbs.
STEP 80
This step may be difficult for the homebuilder but is one of the MOST IMPORTANT
steps in the engine, because it will determine the engine's ignition timing accuracy. If it
isn'-t right, you'll never get your engine to run properly. In FIGURE 90 you see illustrated a tool made up from an old 14mm spark plug. The insulator and other parts
have been removed. A rod is then placed through the plug body with a head on one end
to contact the piston and cotter pin in the other to keep the rod from falling through into
the cylinders. You can make one of these without too much effort and you will never
have to guess where exact "top dead center" is. Two or three degrees either way can
make a big difference in the way your engine performs, and it is virtually impossible to
reference the T.D.C. unless a means is at hand to establish that point. If you have an A
& P type friend, he may have an indicator set-up for this purpose in his tool kit and can
do this job for you.
STEP 81
Clamp a dial indicator onto the head so that it is actuated by the rod in the tool just
described. (SEE FIGURE 91) Now find T.D.C. on that cylinder in the position where
both valves are closed. Do this on the front left cylinder as you face the prop. We are
going to use this one as our #1 cylinder. I am assuming that your prop hub is installed
by now. If not, install it as per manufacturers instructions then complete this step and
the next one.
STEP 82
Find "top dead center," as described in step 81, and set the crankshaft in that position.
Now take a straight edge piece of metal (a brand new hacksaw blade works well) and
align it exactly with the split line in the case. Mark the prop hub flange exactly in line
with the case split line. If you have an electric engraving pencil mark this mark T.D.C.
on the prop flange. Now make another mark 28° clockwise facing the prop on the
flange and mark it well. This is the timing mark you will use to time your magneto.
62
-
•
•
FIGURE 90
FIGURE 95
FIGURE 98
FIGURE 91
FIGURE 92
FIGURE 96
FIGURE 99
FIGURE 93
FIGURE 97
FIGURE 100
FIGURE 94
13
STEP 83
Illustrated in FIGURE 92 is one of the cranl
it end-play adjustment shims. Normal-
ly three of these are necessary to achieve the proper amount of end play, but there is no
way to accurately predetermine just how much shimming will be necessary without
trial fitting. These shims go on the crankshaft against the flange on #1 main bearing and
take up space between that bearing and the flange on the flywheel. (SEE FIGURE 93)
In aircraft we have exchanged the flywheel for a light starter ring or an oil seal rear
hub, but the adjustment procedure is still the same as the stock V.W. procedure. Start
by using 2 only shims on the crank, place the aluminum shim from your gasket set on
the crankshaft end and tighten the gland nut (it holds the flywheel on) to 100 Ft. Lbs.
torque. (SEE FIGURE 96)
STEP 84
Set up an indicator on the front of the crankshaft as shown in FIGURE 9 5 . If you
already have your prop hub on, indicate on the face of it. The results will be the same.
Now use a wooden block and rap the crank to push it to its forward extreme and set
your indicator at " O " there. Next, rap the shaft with your block to its rear extreme and
read the amount it moved on the indicator. If, for instance, it shows movemet of .023,
we know then that to achieve the desireable .006 end play, we have to decrease the
movement by .017 thousandths. Now, remove the flywheel and using your 0" to 1"
micrometer measure the thickness of the two shims you had in it. Lets say they measure
.027 thousandths. We know we need .017 more so the total amount of shim should add
up to .044 thousandths. Now, unless you have access to an ample supply of various
thickness shims, go to your V.W. dealer and get three shims that will add up to
measure .044. Install these shims, retorque to 100 Ft. Lbs. and check the end play.
Between .005 and .008 is allowable for aircraft. If it's not within tolerance, keep going
through the motions until you have it right. IT'S VERY IMPORTANT! When it is
right, remove the flywheel again for the next step.
STEP 85
We must install a crankshaft end seal in the rear of the case around the crank before
final assembly of the flywheel. Note in FIGURE 97 that the seal has a
"U shaped
cross section, and the open side of the " U " faces away from the flywheel on installation. Shims are in place, right? Put the seal in place as shown in FIGURE 99 and using
a block of wood to equalize pressure, drive it evenly into its place in the case. Now,
this is not the approved method for installing this seal, and if you don't k e e p it all
square you will damage the seal. Just go slow and keep it all even, you'll have no trouble. Torque gland nut to 217 Ft. Lbs. NOTE: The last few steps concerning end-play
t4
FIGURE 105
FIGURE 101
FIGURE 106
FIGURE 102
FIGURE 107
FIGURE 103
FIGURE 108
FIGURE 104
65
adjustment, and seal installation do require special tools that are expensive. If you have
a V.W. dealer or local mechanic that works on V.W.'s it will cost you very little to
have him set the end-play, install the seal and torque the gland nut. Be sure, however,
that he uses the .005 to .008 end play tolerance Figures.
STEP 86
Now we will set the valves for clearance. Follow the procedures outlined in the chapter
on "TAPPETS" here.
STEP 87
Install your rocker arm covers. We like the covers that are retained by spring clips
because
the
springs always keep pressure on the gaskets and the best seal is achieved so you don't
get oil leaks. There is no reason you can't use the stock V.W. valve cover either,
though the aluminum covers do help to dissipate some of the heat from the heads and
oil (SEE FIGURE 102, 103, 104, 105)
STEP 88
You will need to have an oil cooler which normally attached to the engine as illustrated
in FIGURE 107. Most of you will find that a remote kit will probably best suit your
needs.
HAPI sells an excellent setup which allows placement of the cooler virtually
anywhere.
STEP 89
In FIGURE 108 you will note a 1/8 N.P.T. threaded hole in the case. This is the point
of attachment for the line on your oil pressure gauge. If you've done everything right,
your engine will idle at about 50 Lbs. oil pressure and run at 70 to 80 Lbs. On initial
start-up, if starter equipped, turn the engine over with the starter, mag & fuel "off,"
until oil pressure is seen on the gauge. If you have to hand prop it, disconnect this oil
line and using a pump type oil can full of clean motor oil, pump until oil galleries are
filled before starting. Of course, be sure to fill the engine with oil!
STEP 90
This last long step is really up to you. There are so many variations in manifolding,
magneto drives, accessory cases and all the other paraphenalia that it is virtualy impossible to anticipate which way you may want to go with your engine. In all cases,
follow the manufacturer's instructions in installing his accessories and you should be
right.
If there are any points that are not clear or haven't been covered, please feel free to
write and explain your problem. HAPI will be glad to try to help if you will please include a self addressed stamped envelope. Please allow a couple of weeks for reply. If
you are really on the spot, call us for a quick answer. Any comments or constructive
66
criticism you may be able to offer after using this book will be appreciated.
HAPI stocks and sells every part of the V.W. engine, plus all of our conversion accessories. All
of our parts inventory is selected for only one purpose; to be reliable in the air. In most cases we can
offer lower prices to you than you will find in local auto parts stores. We are always ready to help
you with our experience. Just call or write if you need help you don't have to buy anything. We
don't ever want anyone to have problems with an engine because he couldn't get help!
67
chapter 9
TAPPETS
Before we actually adjust the tappets, perhaps it would be worthwhile to take the time to understand why we adjust the tappets to so precise a tolerance, and why it is so important.
Valves are our means of opening the combustion chamber and allowing the filling of the chamber
with an explosive mixture of fuel and air that has been premixed in just the right proportions by the
carburetor. We have then ignited this mixture by means of the spark p l u g and harnessed the expansion of gas caused by the resulting explosion in the cylinder. At the bottom of the power stroke the
exhuast valve opens and allows this hot burned gas to exit into the exhaust pipe.
We have been made aware that heating metal causes it to expand. We used this expansion to our
advantage when fitting the cam driver gear on the crankshaft.
The valves in the engine must be set up with a certain amount of a gap or clearance between the
valve stem and tappet face to allow for the increase in length when the valve is heated by the engines
operation. Tappet clearances on the engine are set while cold, and we recommend clearances of
.005 on the intake valves, and .007 on the exhaust valves. Some of you will note that this is a little
more than is used in automobiles, but we work the engine harder and develop more heat, so consequently we need more clearance.
If a valve is set up with insufficient clearance, the heat will increase its length until all clearance is
used, then the valve will be unable to completely close and seal. This is the way that many valves
are "burned". If the valve fails to seal, it can't dissipate the heat. The valve normally dissipates
much of its heat through heat transfer from valve to seat while the valve is "closed", which is about
75 % of the time. If the valve does not seal completely, not only does it leak compression, but it cannot dissipate the heat it normally transfers to the seat. v ery soon it "burns" or warps, and this
causes even more leakage and burn. Once the valve begins to leak, it is almost always irreverseable
without pulling heads and at least hand lapping the valves to again mate the valve to the seat.
Some of the tappet clearance is used by engine heat expanding the pushrods also.
In order to properly set the valves it is necessary to remove the spark plugs. When you pull these
spark plugs it is a very good idea to run a compression check immediately. This is done by running
the engine enough to attain normal operating temperatures, then stopping it, and immediately
68
removing the spark plugs to perform the compression test. All cylinders should register pressure
within 5 lb. spread between the lowest and highest cylinders. This should be done each time you
reset the tappets to assure yourself that all valves are still sealing properly and have not been damaged. When you have finished your compression check proceed with the tappet adjustment sequence
as follows:
NOW WAIT UNTIL THE ENGINE IS COLD BEFORE SETTING TAPPETS!
Find compression on #1 cylinder by placing your finger over the spark plug hole and rotating the
prop until you feel compression, and then bring the engine's "TOP DEAD CENTER" mark, as
was described on page 62, into alignment with crankcase split line. You are now ready to set the
tappets on #1 cylinder. Do this exactly as follows:
A)
Loosen lock nut (13mm) on the tappet adjusting screws until you can turn the screw with a
screwdriver. Hold the wrench in one hand and the screwdriver in the other so you can use them
both simultaneously. The valves nearest the center of the heads are intakes, and the valves on
the ends of the heads are exhaust. Slide a .007 feeler gauge leaf between the tappet and the exhaust valve stem.
Slowly tighten the tappet until a slight drag is felt. That tells you that the two parts are beginning to squeeze down on the gauge. Do not allow the tappet adjust screw to move now and
tighten the locking nut. Take the wrench and screwdriver off and recheck the clearance with
the gauge. If it's too tight you will have to force the gauge in, too loose and the gauge will have
no drag. What you want is just a very slight drag that tells you that any more would be too
tight, any less would not have drag and be too loose.
B) Repeat the exact same process on the intake valve except use a .005 feeler gauge. Since the intake valves don't have to handle as much heat as the exhaust, they don't expand as much. Be
sure you get them tight enough to take up all the slack, and loose enough that the drag on the
feeler gauge in only slight.
C) Rotate the crankshaft turning it clockwise 180° and #2 cylinder will be in position for adjustment. Repeat the above procedure.
D) Again, rotate the crankshaft clockwise 180° or more and #3 will be in position for adjustment.
Repeat adjustment procedure.
E)
Rotate crank 180° again to bring #4 into position for adjustment. Complete adjustment on #4.
F)
Rotate crank 180° to the #1 position. Then go through the other cylinders, rechecking all the
tappets again to be sure none are too loose or too tight.
69
G) Re-install spark plugs.
H) Install the valve corners and then hand prop the engine with the magneto and fuel turned off.
There should be little or no difference on the amount of effort required to pull each cylinder
past compression. If you feel a "soft" one that pulls through easier than the others, go back
and recheck each step to be sure you didn't leave a valve improperly adjusted.
*Tappet setting should be rechecked and reset after each 25 hours of normal operation.
RECOMMENDED TORQUE VALUES FOR V.W. ENGINES
LOCATION
DESIGNATION
THREAD
FOOT
LBS.
Connecting Rod 1-1200
Connecting Rod
Bolt
M 9x 1
22 -25
Connecting Rod, All Other Engines
Nut
M 9x 1
22 -25
Crankcase Halves
Nut
M 12 x 1.5
25
Crankcase Halves
Nut
M8
14
Gland Nut
M 28 x 1.5
217
Prop Hub To Crankshaft
Bolt
M 20 x 1.5
94 - 108
Oil Pump To Crankcase
Nut
M8
14
Oil Cooler Or Bracket To Crankcase
Nut
M6
6
Cap Nut
M6
6
Plug
M 14 x 1.5
25
-
M 10 x 1
7
Breather To Crankcase
Nut
M8
14
Cover Fuel Pump To Crankcase
Nut
M8
11
Cylinder Head To Crankcase
Nut
M 10
23
Cylinder Head To Crankcase
Nut
M8
18
Rocker Shaft To Cylinder Head
Nut
M8
18
Intake Pipe To Cylinder Head (Type 1 & 2)
Nut
M6
6
Intake Pipe To Cylinder Head (Type 3)
Nut
M8
14
Spark Plug in Cylinder Head
-
M 14 x 15
25
Exhaust Pipe Cylinder Head
Nut
M8
16
Flywheel Or Drive Plate to Crankshaft
Oil Strainer Cover To Crankcase
Oil Drain Plug In Cover
Oil Pressure Switch To Crankcase
(Type 1 & 2)
70
chapter 10
TROUBLESHOOTING
SYMPTOM
POSSIBLE CAUSE
Engine Won't Start
Magneto " P " Lead Grounded
Fuel Supply Off
Improper Ignition Timing
Incorrect Valve Timing
Defective Magneto
Spark Plugs Fouled
Plugged Fuel Line
Plugged Carburetor Jet
Engine Flooded
Tries To Start But Kicks or Erratic Firing
Magneto Timing Off
Incorrect Firing Order
Defective Magneto
Defective Magneto Coupler
Incorrect Valve Timing
Starts But Won't Run
Mixture Too Rich (Look for Black Smoke)
Mixture Too Lean (No Smoke)
Inadequate Fuel Supply
Fuel Valve Off
Intake Manifold Leaks
Engine Idles Well Won't Turn Up
Too Rich At Speed (Black Smoke)
Too Lean (No Smoke, Quits)
Good High Speed Won't Idle
Idle Stop Needs Adjustment
Mixture Too Rich (Black Smoke)
Mixture Too Lean (No Smoke)
Engine Misses
Mixture Too Rich Or Lean
Possible Magneto Problem
Spark Plug Lead Failure
Spark Plugs Fouling
Improper Spark Gap
Intake Manifold Leaks
Valve Clearance Problem, Check Tappets
Valve Stuck Open
71
Low Oil Pressure
Engine Low On Oil
Engine Oil Frothing
Defective Gauge Or Line To Gauge
Pressure Relief Valves Incorrect
Defective Oil Pump
Plugged Sump Pick-Up Tube
Bad Seal On Sump Pick-Up Tube
Engine Bearing Failure
Incorrect Bearing Sizes
No Oil Pressure
Defective Gauge Or Plugged Oil Line
No Oil In Crankcase
Oil Pump In-Operative
Broken Sump Pick-Up Tube
Near Total Bearing Failure
Cylinder Head Temp Too Hot
Improper Ignition Timing
Wrong Grade Fuel
Inadequate Air For Cooling
Incorrect Baffling, Cowling
Cowling Air Out-Lets Inadequate
Incorrect Gauge
Oil Temp Too Hot
No Oil Cooler
Inadequate Air For Cooler
Cowling And Baffling Inadequate To Cool
Incorrect Gauge
Engine Vibrates Excessively
Loose Motor Mounts
Prop Out Of Balance
Uneven Compression (Check Valves)
Uneven Firing, Check Ignition System
Fuel Mixture Problem
Check Prop For Correct Tracking and Balance
Manifold Leak Associated With Vibration
Runs Good Won't Turn Recommended Static
R.P.M.
Too Much Pitch On Propeller
Too Much Diameter On Prop
Runs Too Much R.P.M. Static
Not Enough Pitch On Propeller
Not Enough Diameter On Prop
Propeller Doesn't Track Line
Incorrect Propeller Installation
Incorrect Prop Hub Installation
Prop Flange Face Not Square With Shaft
72
NOTE " A "
These earlier type I engines can be converted, but due to small oil galleries in the case (it's basically
the same as the old 40 horse case). The author would suggest that the later type II or III cases be used.
NOTE " B "
Some of these type IV engines have been converted very successfully. What is meant by the authors
statement is that'this book is not to be used as a suitable guide for type IV conversions.
NOTE " C "
V.W. cam gears come in sizes ranging from plus 3 thru minus 3, (plus 3 being the larger size) so it
may become necessary to change cams with a larger or smaller gear to get correct backlash. The
size gear you have is stamped on the rear face (cam side) of the cam gear.
NOTE " D " Most piston and cylinder sets come with a copper base gasket or about .007 thickness.
It can be used as one of your barrel shims, place it next to the case only on final assembly.
NOTE " E "
We find that Silicone Bathtub sealer by General Electric works very well as a cylinder base sealer.
It's unaffected by heat or oil and withstands vibration. Put on a bead the diameter of a wooden
match around the cylinder base and coat the barrel shims with it.
NOTE " F "
Wrist pin keepers or "circlips" sometimes get loose from their grooves and score or ruin cylinders.
We at HAPI are now using teflon wrist pin pads instead. This is simply a teflon plug that occupies
all the space at both ends of the wrist pin and nothing can then get out of position. With the teflon
plugs (IIAPI stocks them about $10.00 a set) the circlips are not used.
Note "G"
At this time H.A.P.I. Engines no longer supplies parts or
sen ices. We suggest thai you contact:
GREAT PLAINS AIRCRAFT SUPPLY CO
P.O. Box 545
Boystown, NE 68010
Info: 402-493 6507
Fax: 402-333-7750
Order Toll Free 800-922-6507
73
NOTE " G "
We have found that in some tightly cowled installations the spring retainer clips occupy too much
room. We now install a "bolt on cover" which is giving good results.
LOOPED TO PROVIDE SOME SPRING
CLIP SHOWN FULL SIZE
Bend ears fit
inside from outside
of case.
LIFTERS
74