Reconditioning valve train components
Knurling valve guides
• For correcting worn guides
• Mostly for integral guides
• Use wear limit of .004” (Use Go/No-Go)
• Fixed arbor or roller
Copyright 2003 Gary Lewis – Dave Capitolo
Reconditioning valve train components
Fixed arbor knurling
• Cold forming tap with pilot
• Produces a thread by deforming metal inward
• Threads are formed, not cut
Reconditioning valve train components
Fixed arbor knurling
• Standard domestic knurls are 5/16”, 11/32”, & 3/8”
• Reamers are sized by thousandths of an inch
Reconditioning valve train components
Knurling procedure
• Use extreme pressure lubrication
• In guide/seat machine or with speed reduction drill
• Clockwise direction only
Reconditioning valve train components
Knurling precautions
• A 3/8” knurl will start in an 11/32” guide
• Removable guides may break
• Once knurl is started, don’t stop
Reconditioning valve train components
Reaming
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Increases inside diameter to proper clearance
Pilot keeps reamer straight
Clockwise direction only
Shallow groove left in guide for longevity
Reconditioning valve train components
Reaming procedure
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Continuous flow of coolant to flush chips
Select reamer  Stem diameter + clearance
When done, reamer should fall out of guide
Counterclockwise rotation dulls reamer
Reconditioning valve train components
Measuring knurled & reamed guides
• Measure knurled guides with bore gauge.
Probe will span grooves
• Set gauge to stem diameter & read clearance
Reconditioning valve train components
Roller knurling
• Single roller used to knurl guide
• Continuous flow of oil
• Diamond hone used to finish guide
Reconditioning valve train components
Replacing guides
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Aluminum heads & some iron heads
Usually removed & installed from port side
Measure height above spring seat
Heat head to 250ºF & add oil around guide
Reconditioning valve train components
Replacing guides
• Tap guide & install cap screw to remove
• Use cap screw technique for bronze guides
• Core drill to create shoulder to drive on
Reconditioning valve train components
Replacing guides
• Before installation, measure!
• Heat head, oil guide & head
• Install to specified height
Reconditioning valve train components
Oversized valve stems
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For correcting wear in integral guides
Sizes include .003”, .005”, .010”, & .015” oversize
Engine manufacturers recommend oversize stems
Economical when guides are worn
Reaming is done incrementally
Reconditioning valve train components
Replacing integral guides
• Valve guide bushing (false guides)
• Allows for upgrading material to bronze
• Replacement guides provide .0015” interference
5/16” guides
7/16” OD
11/32” guides
1/2” OD
3/8” guides
1/2” OD
Reconditioning valve train components
Replacing integral guides
• Precision level is used to align guide to spindle
• Level the guide in two directions
• Core drill to within .025” of replacement guide
Reconditioning valve train components
Replacing integral guides
• Ream to final size
• Core drills and reamers follow the previous hole
• Core drills and reamers use pilots
Reconditioning valve train components
Replacing integral guides
• False guides are driven by air hammer & driver
• Oil guide & bore for installation
Reconditioning valve train components
Replacing integral guides
• Excess length can be trimmed off at either end
• Ream guides after length has been cut
Reconditioning valve train components
Installing bronze liners
• Thin bronze liner for reduced wear rates
Reconditioning valve train components
Installing bronze liners
Production installation
• Ream .030” oversize with coated reamer
• Driven in place with installation tool
• Liner is expanded & sized with burnishing tool
• Excess length is trimmed
• Brush type hone gives crosshatch
Reconditioning valve train components
Installing bronze liners
Occasional installation
• Bore guide using drill motor
• Liner driven in using hammer & driver
• Excess liner is removed
• Knurling locks liner in place
• Reamed to size
Reconditioning valve train components
Refacing valves and stems
• To remove all pits from face & stem
• Grinding sequence can be different between machines
Reconditioning valve train components
Refacing valves and stems
• Interference – Thins margin less
• Check for bent valves during machining
Reconditioning valve train components
Refacing valves and stems
• Chamfer tips to 1/32”
• Grind .003”- .005” from tip
Reconditioning valve train components
Refacing valves and stems
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Dress grinding wheel
Use oil between wheel & valve
Back & forth grinding action
Back wheel off when done
Reconditioning valve train components
Grinding valve seats
• Purposes:
Remove pits
Proper seat width
Uniform seat width
Seat position on face
• Check seat inserts for looseness
• Seats are machined concentric to guides
• Guides serviced before seats
Reconditioning valve train components
Grinding valve seats
• Seat width
Too wide – Traps carbon & causes burning
Too narrow – Insufficient heat transfer &
causes burning
• Seat width specs
2 valve heads - .060” to .090”
smaller valve heads - .040”
Contacts slightly above center on face
Seat width must be uniform
Reconditioning valve train components
Grinding valve seats
• Contact position on valve face
Too high – Burning through thinnest part
Too low – Poor sealing
Reconditioning valve train components
Seat grinding stones
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Stones should be 1/8” larger than valve head
Select 30 º, 45º, & 60º stones
30 º stone that is too small forms a groove
Roughing & finishing stones
Reconditioning valve train components
Seat grinding set up
• Install correct size pilot,
with pilot wrench
Reconditioning valve train components
Seat grinding procedure, method #1
If spring & stem height are a concern
• 45º - Grind seat angle first to remove pits
• Redress stone as needed for surface finish
• 30º - Grind the top angle & check position
Reconditioning valve train components
Seat grinding procedure, method #1
• Make corrections with 45º & 30 º as needed
• 60º - Grind bottom angle to narrow seat width
& make seat width uniform
Reconditioning valve train components
Seat grinding procedure, method #2
For seats that require minimum machining
• 30º - Grind top angle until seat angle narrows
• 45º - Grind seat angle to clean up
• Check position with Prussian Blue
Reconditioning valve train components
Seat grinding procedure, method #2
• 60º - Grind bottom angle to narrow seat
• Check width with Prussian Blue
Reconditioning valve train components
Checking seat concentricity
• Prussian Blue in a few places & do not rotate valve
• Concentricity gauge
Reconditioning valve train components
Valve & seat wear
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Poor lubrication with unleaded fuel
CNG has less lube than unleaded
Other engine parts wear less with CNG & unleaded
Remove valve rotators in CNG engines
Cobalt alloy seats & Inconel valves in CNG engines
Reconditioning valve train components
Cutting valve seats
Adjustable carbide inserts
• 30º then 45º for reduced chatter
• Driven by hand or by low speed drive motor
Reconditioning valve train components
Cutting valve seats
Three angle cutting system
• Increased precision & productivity
• Grinding stone may be used to touch up seat
Reconditioning valve train components
Cutting valve seats
Three angle cutting system
• Position pointer on valve face for contact point
• Adjust cutter to same position
• Seat width is determined by the cutter
Reconditioning valve train components
Cutting valve seats
Three angle cutting system
• Seat angles being cut in guide & seat machine
Reconditioning valve train components
Cutting valve seats
CNC machine
• Seat angles being cut in CNC machine
Reconditioning valve train components
Installing valve seats
For crack repair & seat recession
• If .060” shim can’t correct spring height
• If stem height can’t be corrected by grinding tip
Reconditioning valve train components
Installing valve seats
Seat selection
• OEM seats may be induction hardened
• Use hard seats with alloy valves for propane
• Heavier duty seats for recession
Reconditioning valve train components
Installing valve seats
Seat selection
• Aftermarket seats listed by:
OD
ID
Depth
• Materials include:
Cast Iron
High-nickel chrome alloy
Hard alloys
Reconditioning valve train components
Installing valve seats
Seat selection
• Interference = seat diameter – cutter diameter
• For integral seats, select seats by application
Reconditioning valve train components
Installing valve seats
Removing the original seat
1. Weld an old valve to seat & drive seat out
2. Weld a bead on the inside of the seat, cool, & remove
Reconditioning valve train components
Installing valve seats
Removing the original seat
3. Bore old seat to a thin shell
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Hard seats dull cutters!
4. Weld a bead on the inside
of the seat, cool, & pry
Reconditioning valve train components
Installing valve seats
Installing a replacement seat
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Inspect bore for damage & measure ID
(Damaged bores cause unequal cooling)
If bore is within specs, install new seat
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If bore is out of specs, install oversize seat
Reconditioning valve train components
Installing valve seats
Installing a replacement seat
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Clean bore & lubricate seat to prevent galling
Install with chamfered edge down
Aluminum heads may be heated
Install with driver & hammer, using pilot as a guide
Reconditioning valve train components
Installing valve seats
Replacing integral seats
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Choose cutter for proper interference
Set depth of cut to match the seat thickness
Set spindle speed & bore
Reconditioning valve train components
Installing valve seats
Replacing integral seats
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Grind seat angle to installed height
Then grind top & bottom angles for position
Reconditioning valve train components
Fitting valve seals
Types of valve seals
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O-ring – Fixed to valve, lower groove, no sealing
Umbrella – Fixed to valve, no sealing
Positive – Fixed to valve guide, positive sealing
Reconditioning valve train components
Fitting valve seals
O-ring installation
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Compress spring to expose lower groove
Install seal
Install keepers
May have oil shield
Reconditioning valve train components
Fitting valve seals
Umbrella installation
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Install seal onto valve stem
Install spring
Compress spring
Install keepers
Reconditioning valve train components
Fitting valve seals
Positive seal installation
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Machine top of guide to . . .
- Reduce OD
Leave 3/16” between top of
- Reduce height
guide & bottom of retainer
- Chamfer top
Reconditioning valve train components
Fitting valve seals
Positive seal installation
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Use plastic sleeve for installation
Use installation tool
Adjust spring compressor to prevent seal damage
Reconditioning valve train components
Fitting valve seals
Seal materials
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Nitrile – OEM, 250ºF
Polyacrylate - 350ºF
Viton - 440ºF
Reconditioning valve train components
Replacing rocker arm studs
Press fit studs
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Spacer & nut
Hydraulic puller
Reconditioning valve train components
Replacing rocker arm studs
Oversized studs
• +.003” or larger
• Ream to .001” to .003” press
• Install to proper height
Reconditioning valve train components
Replacing rocker arm studs
Threaded studs
• Thread square to existing hole
• Spot face top of hole
Reconditioning valve train components
Installed SPRING height
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Measure from spring seat to bottom of retainer
Use shims to correct
Reconditioning valve train components
Installed SPRING height
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Use .030”, .060”, or no shim at all
Goal is +/- .015” of specifications
Reconditioning valve train components
Spring warnings
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Make sure spring compresses more than valve lift
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Progressively wound springs
- Reduce high frequency oscillations
- Reduce valve float
- Tight end faces down
Reconditioning valve train components
Installed STEM height
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From spring seat to tip of stem
Correct by facing tips in valve grinder to match ends
If no specs, use measurements from disassembly
Reconditioning valve train components
Installed STEM height
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Shorter push rods can correct height
Shim type OHC warning
Reconditioning valve train components
Refacing rocker arms
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Forged & cast rockers only
Check rocker shafts clearance first
Reconditioning valve train components
Straightening Aluminum Heads
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Heads expand in all directions
Heads warp upwards
Reconditioning valve train components
Straightening Aluminum Heads
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Straighten head based on the top side
Check cam for binding
Reconditioning valve train components
Straightening Aluminum Heads
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Check seat-to-guide alignment
Straightening heads:
- Reduces surfacing
- Improves seat alignment
- Improves cam alignment
Reconditioning valve train components
Straightening Aluminum Heads
Stress relieving
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Heat treating process to relieve stress caused by warp
Requires 500ºF for 4 hours
Slow cooling restores precipitation hardening
Properly fitted seats should not fall out
Reconditioning valve train components
Straightening Aluminum Heads
Stress relieving preparation – pushrod cylinder head
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Measure head warp on deck surface
Use shims at each end equal to the amount of warp
Torque nuts to no more than 25 lbs/ft
This should bend head into alignment
Reconditioning valve train components
Straightening Aluminum Heads
Stress relieving preparation – OHC cylinder head
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Measure head warp in cam bore
Use shims at each end equal to half this amount
Torque nuts to no more than 25 lbs/ft
Reconditioning valve train components
Straightening Aluminum Heads
Stress relieving preparation – OHC cylinder head (cont)
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Recheck alignment & adjust shims as needed
Reconditioning valve train components
Straightening Aluminum Heads
Stress relieving procedure – OHV & OHC
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Place head in oven for 4 hours
Allow to cool slowly
Reconditioning valve train components
Straightening Aluminum Heads
Stress relieving procedure – OHV & OHC (cont)
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OHV surfacing is minimal
OHC surfacing may be more
Reconditioning valve train components
Correcting Overhead Cam Centerlines
Removable bearing supports
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Top of the head can be surfaced
Shims installed under supports
Reconditioning valve train components
Correcting Overhead Cam Centerlines
Removable bearing caps
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Can be line bored
Caps are ground
Housing bores are bored to standard or oversize
Reconditioning valve train components
Correcting Overhead Cam Centerlines
Removable bearing caps
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Minor wear – Fixed by polishing
To reduce clearance – Lap bearing cap
Plastigage on assembly
Reconditioning valve train components
Correcting Overhead Cam Centerlines
Integral bores
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Can be line bored oversize
Oversize cam journals or bearings
Reconditioning valve train components
Regrinding camshafts
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Inspect:
• Cam lobe wear
• Fuel pump eccentric
• Distributor drive gear
Reconditioning valve train components
Regrinding camshaft
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Lift & duration can be maintained
Reconditioning valve train components
Regrinding camshaft, preparation
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Check straightness
Set up grinding masters
Grind similar tapers, then opposite tapers
Reconditioning valve train components
Regrinding camshaft
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Each lobe must be indexed
Amount & direction of taper is ground into lobes
Grind similar tapers, then opposite tapers
Reconditioning valve train components
Regrinding camshaft
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Scuff resistant coating is applied to cam
Highly polished surface is preferred
Reconditioning valve train components
Lifter base grinding
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Lifters & bucket followers can be reground