This series will show many firsts again. The T Bird Pro Stock that I designed in 1982-3
was responsible for my un-retirement of sorts. Having been through 2 years of
chemotherapy, I was somewhat pleased with my job at General Dynamics. I was working in
propulsion and the number of shapes that we were playing were the same, or less efficient
than those I'd developed for heads and manifold runners over the years. Keep in mind that
ENDYN was still cranking away and my sole reason for taking a breather was because my
doctors felt that ENDYN's "environment" and long hours could have contributed to
my cancer.
One day, an acquaintance asked me if I'd ever consider building another Pro Stock car
again. After a brief moment of thought, I felt that I deserved to do something for
"me" again, and the project was born. This is also where I decided to do what I
wanted again, doctors or not.
After all the years racing and watching customers, I had some different ideas regarding
"how" I'd reenter the sport's most difficult class. The "normal"
amount of between-round thrashing wasn't for me, but sitting in a comfortable chair
drinking tea while waiting for the next round was an appealing thought.
In order to achieve that end, running a conventional Pro Stocker was decidedly not
going to cut it. A complete rethink of the ingredients was necessary and ultimately, every
component produced (including the low revving engine) was quite unlike anything ever
created for the class, before or since. To use Mark Donahue's words, we needed an
"unfair advantage." The following is a brief attempt to touch on a few of our
"interpretations" of how a Pro Stock car should be built.
Having been long associated with Ford, the new 83 T Bird looked like a pretty good
starting place to me. Ford sent me lines drawings for the new car and the project began in
full. I built a wind tunnel that had a rolling floor and began testing a quarter scale
model that I made from the lines. The drag coefficient was not bad, but the amount of lift
that the car exhibited at speed was terrible. By spoiling the lift, the drag went to pot,
but worse, the car also was a lifting body whenever it was not traveling in a perfectly
straight line. This may seem strange to drag racing fans, but Pro Stock cars travel a lot
of the track at small slip angles and if the car really got loose, it could present it's
entire side body to the airflow, with disastrous results.
The first project at hand was to make it harder for the air to pass over the sides of
the car. From the roof back, some 1/8th inch welding rod swept into the "side to
trunk" intersect cause so much turbulence that there was no longer negative pressure
present and the car staid stuck. The best part was that nobody could see the change and we
shared it with some select NASCAR teams with no fear of detection by inspectors.
In order to lower the car's drag, there were some rather dramatic engineering exercises
necessary that had never been applied to a full bodied drag car before. I made the
decision that we'd try to take advantage of the air rather than fight it. The goal was to
create efficient ground effects by encouraging air to travel under the car, instead of up
and over the body.
The first thing to go was the chin spoiler that was on all T Birds. This was relatively
easy to do. The design and construction of tunnels under each side of the car with skirts
preventing air from bleeding to the driveshaft tunnel consumed a lot of model testing and
real world ingenuity, especially since aero devices under the car were prohibited by the
rules.
More testing revealed where we should locate the venturi sections for optimum
aero-loaded weight distribution. To complete the venturi shapes, the air was channeled
between the rear tires and into the "air chute" at the rear of the car. Aside
from simply rerouting the air, we were able to prevent the rear slicks from running over
air at the rear as well. Eventually we even filled the "voids" in the front of
the 9" third member with lightweight epoxy and micro-balloons to ease the flow around
the rear end.
The rules didn't permit cutting the rear bumper area on the car, unless it was done for
wheelie bar clearance. Since we needed the area for the air chute exit, I designed the
wheelie bars to be long enough to require the surgery.
Building the real "thing" consumed about 4 months of continuous work, but
keep in mind that the finished piece was the result of months of tunnel time and we also
built several full-scale "models" to insure that the package was workable.Since
we'd defined the optimum aero-envelope, the engine and chassis also had to fit inside the
shape, or we'd have achieved nothing, and this was also a primary reason for the
full-scale mock-ups.
When tested in the real world, our aero expectations were more than met and there were
no spoilers. At 60 mph the car had increased from 2350 lbs to 3100 lbs, at 100 mph the
weight was 3350, at 160 mph the weight was 3850, and at 195 mph we peaked at 4800 lbs,
while maintaining a constant aero induced 38/62 weight distribution. This placed the cg
directly under the driver's ass and we actually put the bottom of the seat lower than the
floor in the car, making it a "legal" part of the venturi tunnel.
To make the car as efficient as possible, I took some liberties with the rules,
especially the ones regarding sectioning the body. Some of the illegal body alterations
included removal of 1.5" in body width, beginning with none in the rear, and tapering
to the inch and a half at the nose. This required sectioning a long pie shaped piece from
the top surfaces of the car. The doors were sectioned to yield a straight line intersect
between the rockers (outside skirts) and the spoilerless nose piece.
The wheel wells were "moved" on all corners and reshaped considerably. The
front of the forward wheel wells was designed to help "influence" the air to
attach to the sides of the car behind the wheel well and simultaneously bleed some air
into the well's trailing edges to provide more air for work in the tunnels under the car.
At the rear similar treatment was performed with some outside air used to help blow the
boundaries (act as fences) for the air exiting the rear chute section. There were only a
few body templates to meet in those days and my old saying "If you change something,
change everything else and the templates will fit" worked to perfection. In order to
help with some of the visual effects, we used 10 or 12 shades of white to make "small
areas" look larger and "large areas" look smaller. Out optical illusions
worked to perfection, as nobody ever mentioned any funny looking areas of the car.
