Top 10 Pro Stock Innovations
A list of the major developments that transformed Detroit’s factory hot rods from
nine-second near-stock vehicles to today’s 6.5-second, 211-mph entries
T
he original Pro Stockers that debuted at the
1970 Winternationals would compare closest
with today’s Stock entries. Built entirely from
production bodies with only three-point roll bars,
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stock front and rear suspensions, and nine-inch
tires, these vehicles bore little resemblance to
today’s highly sophisticated tube-chassis
counterparts, which are powered by 500-cid engines
Clutchless four-speed Lenco transmission
During the first three Pro Stock seasons, the transmission of choice was the manual four-speed,
a carryover from the handicap Super Stockers and the match race A/FX cars of the mid-1960s,
but the breakage-prone manual transmissions required a high degree of maintenance at a
tremendous cost. As elapsed times approached the low-nine-second range, only a handful of
drivers could drive a four-speed with any degree of consistency. When the Lenco transmission,
which allowed gear changes without the use of the clutch, was introduced at the 1973
Winternationals, most teams had switched to the new design by the conclusion of the rainpostponed event. Gifted four-speed drivers such as Ronnie Sox and Don Nicholson, whose times
actually slowed with the Lenco, objected to the new transmission, but with so many more drivers
benefiting from the clutchless design, the Lenco was used for many years before it was replaced
by the even more efficient models produced by G-Force and Liberty.
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In a revival of the popular A/FX match races of the mid-1960s, racers such
as Bill Jenkins, Don Nicholson (pictured), and Dick Landy and the Sox &
Martin team began converting their handicap-start Super Stockers and A/MP
entries into heads-up match race machines with 427-cid engines. Their
spectacular nine-second runs with a full-bodied production car caught the
imagination of fans and inspired the creation of Pro Stock in 1970.
Car Craft magazine
Bill Jenkins’ ’72 Vega
Jenkins won the first two national events of the 1970 season with his ’68 Camaro, but Dodge and
Plymouth entries triumphed at the remaining five events that year and won seven of eight in
1971. Concerned that domination of Pro Stock by one brand might cause fans to lose interest in
the category, NHRA introduced weight breaks for the 1972 season that allowed small-block wedge
engines to run at 6.75 pounds per cubic inch, canted-valve wedge engines at 7.00 pounds per
cubic inch, and big-block Hemis at 7.25 pounds per cubic inch. Jenkins showed up at the 1972
Winternationals with a ’72 Vega that featured a tube-chassis frame with a roll cage, though the
stock A-arm front suspension was still retained. The combination proved to be nearly unbeatable.
Jenkins defeated five Hemi-powered entries in the Winternationals’ 32-car field and won five of
the remaining seven events that year in the most successful season of his career.
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that produce approximately 1,400 horsepower. The
following are the 10 more significant developments
in the evolution of Pro Stock.
1969 “heads-up” Super Stockers
When Super Stock was introduced in 1967, the category featured a variety of classes and
cars competing with handicap starts that were based on national records. But fans of the
popular match race circuit back then preferred heads-up action, so the top Super Stockers,
such as the SS/B Hemi Darts and Barracudas, raced against 427-cid big-block A/MP
Camaros and 427-cid SOHC A/MP Mustangs. Racing at a weight break of seven pounds per
cubic inch, these cars put on dazzling displays of rosin burnouts and nine-second runs
despite weighing nearly 3,000 pounds. NHRA quickly reacted to this exciting concept and
announced at the 1969 World Finals in Dallas that a new heads-up category, Super Stock
(eventually renamed Pro Stock), would debut at the 1970 Winternationals. The rules were
nearly identical to those employed by their 1969 predecessors; the use of fiberglass hoods,
fenders, and a hood scoop were the only modifications allowed to the otherwise stock bodies.
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by John Jodauga
Though it still used a stock
front end with factory A-arm
front suspension, Jenkins’
’72 Camaro is largely
credited as being the first
tube-chassis Pro Stock car.
It also featured a full roll
cage, a significant
advancement over the threepiece roll bars that were
initially used in 1970.
The Lenco transmission, which
used a separate lever for every
gear, was a planetary-type
design that did not require the
clutch pedal to be depressed
for shifting. First introduced at
the 1973 Winternationals, it not
only reduced breakage and
maintenance costs but also
allowed many more drivers to
run as quick as the most
skilled four-speed
campaigners.
Bill Jenkins’ ’74 Vega
Jenkins may have won more races with his ’72 Vega, but his ’74 model was his most
innovative entry. Among the car’s more prominent features was the use of a dry-sump oil
system, a first for drag racing applications, and the introduction of the McPherson strut
front suspension; both features are standard in today’s Pro Stockers. The dry-sump design
was instrumental in producing major horsepower gains. The lowered front ends of the Pro
Stock cars left little room for a deep sump pan, which subjected the crankshaft to the powerrobbing process of sloshing through the engine oil, but with the dry-sump system, most of
the oil is stored in a remote oil tank, allowing the crankshaft to rotate freely without any
contact with excess oil. The McPherson struts, developed by Jenkins and Roger Lamb, not
only provided a lighter and more stable front suspension than the stock A-arm designs but
also created more room that allowed more leeway in exhaust-header design to provide even
more horsepower gains.
Few cars featured more lasting innovations than Jenkins’ ’74 Vega. With
it he introduced the dry-sump oil system to drag racing and the
McPherson strut front suspension, which was vastly superior to factory
A-arms and torsion-bar designs.
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Gapp & Roush four-door Maverick
NHRA continued to refine its weight-break format to include wheelbase factors,
which allowed cars that had wheelbase dimensions longer than 105 inches to run
with less weight. The Gapp & Roush Ford team noted that the new rules allowed it
to run at 6.45 pounds per cubic inch with a car that had a long wheelbase, as
opposed to the 6.80 factor for shorter cars, such as the conventional Pinto. The team
commissioned Don Hardy to quickly build a 108-inch-wheelbase four-door Maverick,
which made its debut at the 1974 Summernationals. Running with 125 to 130
pounds less weight than the Pintos, the team had the quickest car in eliminations
and easily reached the final. Only a huge holeshot by final-round opponent Larry
Lombardo kept the team from the winner’s circle; Lombardo drove Bill Jenkins’
Vega to a 9.11 to 9.02 win. Weight breaks continued to be a major element in Pro
Stock competition for many years until they were replaced by the 500-cid heads-up
format that was established for all brands in 1982.
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When NHRA allowed lighter weight breaks for cars that had a wheelbase of 105
inches or longer, the Ford team of Wayne Gapp and Jack Roush wasted no time in
taking advantage of the rules by quickly building a four-door Maverick, which became
known as “the taxi.” Bob Glidden and Nicholson also took the same path with the
longer-wheelbase ’70 Mustangs.
Kick-out oil pans
S-A Design
The advantages of a dry-sump oil system were known long before they were
introduced to drag racing applications in 1974, but the benefits of the kick-out oil
pan were accidentally discovered. David Reher and Buddy Morrison were attempting
to film the pattern of oil flow within the crankcase using special pans that had
Plexiglas windows. After the window repeatedly fogged up, they removed the pan
from the engine and placed it on the floor and used an extended oil pickup. During
the filming process, someone happened to look at the dynamometer instruments and
noticed a tremendous gain in power. This told them that even with the use of a drysump system, oil bouncing off the sides of the pan and back onto the crankshaft was
still reducing power, so they designed an oil pan that was as wide as possible to fit
within the chassis framerails. Significant power gains were soon realized.
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500-cid rule
By 1981, the weight-break formula had been expanded from engine types (wedge,
canted-valve, and Hemi designs) to each factory brand and size. Because 11 different
engines received their own specific weight breaks, there were 22 weight-break
designations at the beginning of the 1981 season. These factors were subject to change
throughout the season, and it seemed that any time a team gained in performance, it
was penalized with a heavier weight break. Drivers complained that those who worked
the hardest were being penalized the most. NHRA officials and factory representatives
from Detroit agreed that the system had become too cumbersome for racing teams
and fans, so the 1982 rules were changed to dictate that all cars run engines at a
maximum cubic-inch displacement of 500 and that car weight be a minimum of 2,350
pounds including the driver. The complaints and protests ended immediately, and Pro
Stock was propelled into the seven-second zone overnight; the national record was
lowered from 8.23 to 7.82 at the season-opening Winternationals.
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The kick-out oil pan, which
provided more room on the
side of the pan that received
the oil tossed from the
crankshaft, cut down on the
power normally lost by the
oil droplets bouncing back
onto the crankshaft.
The last major change to
the Pro Stock rules took
place in 1982, when NHRA
replaced the increasingly
cumbersome weight-break
formula with the
introduction of the 500-cid
mountain motors. All cars
were required to run at a
minimum weight of 2,350
pounds including the driver.
Frank Iaconio won the first
race under the new format,
at the 1982 Winternationals.
DRCE engine series
Though sophisticated tube-chassis designs had been on the Pro Stock scene for many
years, until the early 1980s racers still relied on radically modified versions of
production blocks and cylinder heads, a very costly process, especially in the case of
the small-block Chevys and Fords, which used cast-iron heads. But this changed in
the mid-1980s with the introduction of the Oldsmobile Drag Racing Competition
Engine (DRCE), which was developed under the leadership of Dave Jarrard, who
worked with a number of leading engine builders and cylinder-head experts to
develop the first factory-produced 500-cid drag racing engine. The first DRCE engine
was debuted at the 1983 Gatornationals and featured siamesed cylinders with thick
walls and a priority oil system. The heads had symmetrical ports, as opposed to the
production big-block Chevy heads that used a combination of short and long intake
runners. The heads were also produced with small combustion chambers and intake
and exhaust ports to give engine builders more leeway in creating their
modifications. Greg Anderson and Jason Line used the latest version of this engine
design, the GM DRCE-3, to produce record-breaking 211-mph runs at this year’s
ACDelco NHRA Gatornationals.
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Detroit’s increased interest in quarter-mile competition resulted in the production of
the first factory-developed 500-cid engine for drag racing, the Oldsmobile DRCE.
Pictured is the engine campaigned by Warren Johnson in 1984. Johnson helped
provide input for the engine’s design. Note that this was before W.J. began covering
up his intake-manifold runners.
April 6, 2007 ✦ 63
from page 63
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Aero hood scoop
Hood scoops, an iconic symbol in Pro Stock, have been on the scene ever since the
class’ creation. The first designs were the rear-inlet “mailbox” scoops used by
Chevrolet racers and the boxy “snorkel” scoops used by Dodge and Plymouth
teams. The tall dimensions of the tunnel-ram intake manifold required large
scoops, and though the scoops provided adequate air to the engine, they created a
significant amount of aerodynamic drag. In the mid-1980s, GM officials conducted
wind-tunnel tests to create a hood scoop that would be integrally engineered with
the airflow characteristics of the car’s body to minimize aerodynamic deficiencies.
Hood scoops became standard equipment on Pro Stockers by 1986, and various
refinements of their design are still used.
The aero scoop, first used
extensively in 1986, was an attempt
to cut down on the aerodynamic drag
created by the previous models,
which had a more boxy design. The
shape was developed in wind-tunnel
tests and was integrated with the
car’s basic airflow characteristics to
increase top-end speeds.
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Raised power bands
A main reason for Greg Anderson and teammate Jason Line combining to win 19
of 23 events in 2004 was their use of engines with a power band that was raised
within the rpm range. This concept had been around for years and is based on the
basic principle that the higher an engine is revved, the more combustion strokes
are produced, resulting in more power to the rear wheels. And though this theory
has not been a secret, successfully implementing its principles requires extensive
work in camshaft and valvetrain design and integrally engineered changes in the
induction system and cylinder heads. Running a 500-cid engine at more than
10,000 rpm also takes its toll on the longevity of parts. Anderson and Line’s
success in employing this concept has resulted in new speed records, from 205.57
to 207.18 mph in 2004 and from 209.75 to 211.69 this season, and four
consecutive NHRA Pro Stock world championships.
Greg Anderson and Jason Line
raised the bar for Pro Stock
engine builders when they
increased the engine power band
to a higher rpm level in 2004. It
was a difficult assignment that
required a massive engine
redesign, but the effort resulted
in 19 victories in 23 events for
the team that year.
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