Acid-Dipped Bodies
When Less Car Meant More Speed
By 1967, Roger Penske and Mark Donohue had a problem with their Trans-Am Camaro. It was fast, properly prepared and carrying too much Chevrolet around with it. Every extra pound had to be accelerated down the straight, dragged through the corners and stopped again at the other end.
The easy weight was already gone. Back seat, sound deadener, unnecessary brackets and whatever else Chevrolet had installed for people who weren’t planning to spend Sunday afternoon chasing Mustangs had been dealt with. Unfortunately, most of the weight still left in the Camaro was the Camaro.
That was inconvenient because the rules required the frame, driveline, suspension and steel body to remain. Trans-Am was supposed to feature production-based cars, not fiberglass race cars wearing Chevrolet emblems and hoping nobody asked rude questions.
The rule said the body had to remain steel.
It did not say how much steel had to remain in the steel.
Now We’re Getting Somewhere
Cutting chunks out of the body would have been obvious. Drilling several thousand holes would have attracted attention from even an inspector working before his second cup of coffee. Penske needed the panels to remain present, recognizable and technically steel while somehow weighing considerably less than Chevrolet had intended.
The answer was chemistry. Acid eats steel, Penske had steel he didn’t want, and introductions were made.
The Camaro body and other steel pieces went to Lockheed Aerospace in California. Instead of cutting away visible sections, chemical dipping reduced the thickness of the metal itself. The roof remained a roof, the doors remained doors and the quarter panels stayed exactly where an inspector expected to find them.
There was simply less Camaro hiding inside every Camaro-shaped piece.
When the job was finished, the car had dropped from roughly 2,920 pounds to around 2,550. Nearly 400 pounds of Chevrolet had disappeared without anybody having to explain why daylight was coming through the doors.
Racers will spend an entire winter drilling brackets, shortening bolts and deciding whether a washer has become an unnecessary luxury just to lose a few dozen pounds. Penske had misplaced close to 400 while keeping the roof.
There was a reason Chevrolet had used thicker sheet metal, of course. Cars are generally expected to remain shaped like cars. Once enough steel had been chemically removed, the Lightweight Camaro began developing the structural enthusiasm of a beer can.
Donohue was still expected to sit inside it while bouncing over curbs, braking hard and treating the thing in ways no Chevrolet salesman had mentioned during delivery. A roll cage went in to stiffen the car back up. Some weight returned, but at least this weight was earning its ride instead of loafing around in a door skin.
Winning Is How Inspectors Learn Your Name
The Camaro became known as the Lightweight, and by late 1967 it was winning. Nothing improves technical inspection quite like beating everybody who already passed it.
A car circulating politely in the middle of the field may enjoy considerable privacy. Start winning and suddenly six fellows with clipboards want to know why your supposedly ordinary Camaro weighs about as much as the other fellow’s toolbox.
The SCCA eventually started paying more attention to the car than the lap times. Once the body panels became thin enough to invite questions about whether Chevrolet had secretly started stamping Camaros from pie tins, the trick had reached the end of its useful secrecy.
The Lightweight was declared illegal for further SCCA competition.
That should have ended the story.
Roger Penske had another race coming.
One Legal Camaro. Two Trips Through Inspection.
At Sebring in 1968, Penske arrived with two Sunoco Camaros. One was a legal, full-weight 1968 car. The other was the banned Lightweight dressed with a 1968 grille and taillights, which was roughly the automotive equivalent of giving a wanted man a new necktie and expecting the sheriff to lose interest.
Both entries needed to clear technical inspection. Putting the Lightweight on the scales would have made the entire exercise rather short, because 370 missing pounds are difficult to explain as a rounding error.
So the Lightweight stayed away from the scales.
The legal Camaro went through inspection wearing one number. Back at the garage, the crew changed the number and sent the same legal Camaro through again. Two entries now had inspection approval, and only one actual Camaro had bothered doing the work.
The Lightweight never saw the scales.
No hidden switch. No secret compartment. No exotic piece of race-car engineering. The legal car simply passed inspection twice so the illegal one wouldn’t have to do it once.
There are racing problems that require wind tunnels, dynamometers and engineers with several degrees hanging on the wall.
This one needed number tape.
And Yes, the Skinny One Was Faster
The Lightweight was about 1.5 seconds per lap quicker than the legal Camaro at Sebring. That is not the sort of advantage requiring a calculator and three engineers to explain. A second and a half is the sort of difference that makes everybody in the neighboring garage start wondering which parts of their own car are still unnecessarily attached.
Donohue and Craig Fisher drove the Lightweight to the Trans-Am class victory in the 12 Hours of Sebring and finished third overall behind two Porsche prototypes. Dissolving a substantial portion of the car had turned out to be a perfectly sound racing decision.
So nearly 400 pounds disappeared. The car got caught. It was banned. It came back wearing a new necktie and fake moustache, while the legal Camaro went through inspection twice to keep anybody from weighing the one Penske actually intended to race.
That is the difference between reading a rule and reading what the fellow who wrote it hoped you would understand.
The rulebook said steel.
Penske gave them steel.
Just considerably less of it than Chevrolet had.