Fantastic Plastic: Corvettes In Racing

To our knowledge, this 1988 piece by the late Len Frank has never been previously published.

PUSHING THE ENVELOPE

THEN: The first Corvette was crude—not very promising as an instrument to take on the best production sports cars in the world. In fact, it looked as if they might have a rough time just being able to handle Ford’s new Thunderbird on the road or the showroom floor.

NOW: After a Corvette won the last race of the SCCA’s Escort Endurance Series in 1987, the SCCA changed the rules to exclude Corvettes. Despite allowing quasi-production cars (like the Porsche 944 Turbos with the Club Sport option, the Ferrari 308GTB and 328 Quattrovalve, the Maserati Bi-Turbo, the Porsche 911, etc.) to compete, the 1984/87 won every one of the races.

What happened between the first Blue Flame Six-and-Powerglide Corvette of 1953, and the last SCCA-eligible Z-51 Corvette of 1987 can be broken down into a few experimental cars, a few failed racing cars, and a stream of steadily improving production hardware—and secret weapons.

The Corvette had two secret weapons: the wonderful all-conquering Chevy small block, and a European émigré’ named Zora Arkus-Duntov. The V-8 was first installed in 1955—a passenger car engine that was designed to be inexpensive to build. It now makes well over 100 bhp/liter in racing trim, and shows no sign of being near the end its of development. It is the one element that runs throughout the Corvette saga. Duntov, who was allowed to stay longer at one job—even past normal retirement—than was thinkable at GM, left before the newest series of production Corvettes was officially begun, got to Chevy about the same time as the V-8.

There was another side–the Corvette seemed bring out all of the GM corporate conservatism, all of the gray-suited penny-pinching, status-quo lovers that embody all of what every enthusiast hated most about Detroit. Too often the efforts of Duntov and other friends-of-the-Corvette were directed toward circumventing a full upper-management press determined to get rid of what they saw as a low volume, low profit embarrassment.

THE HARDWARE

1. SMALL BLOCK V-8. It combined short stroke, low reciprocating weight, very light (for a pushrod engine) valve gear, low overall weight, with good breathing and constant development.

The first Duntov-cammed versions were good for 7000rpm and 250bhp (SAE gross)from 265 cu.in. A current 366 small block built for racing has 600 to 700 net hp, normally aspirated, on racing gasoline.

2. FUEL INJECTION. f.i. was really intended to improve volumetric efficiency, increase fuel economy, and reduce air pollution. The only other significant f.i. car at the time, the 300SL, was made in tiny numbers compared with GM’s Rochester-equipped Chevys. Chevy’s (and Pontiac’s) injection was constant flow rather than the timed Bosch mechanical injection used by MBz, much better suited to volume production but still requiring more precision and quality than the corporation liked. The ultimate f.i. small block was good for 375hp from 327 cu.in. used in 1964/65.

3. SS. The Corvette’s debut in international racing was at the Sebring 12-Hour in late March 1956. Three were entered, two more-or-less production cars, and a modified car that eventually became the SR-2. They didn’t win, or even come close, but what became clear was that a production Corvette, no matter how modified, couldn’t compete with purpose-built racing cars like the Jaguar D and the Ferrari Monzas.

By Sebring 1957, with their budget bolstered by Bill Mitchell’s styling department, Duntov and crew had produced a space-framed (like a 300SL or SLR), magnesium-bodied, slippery (same aero drag a D-Jag), bubble-topped roadster with DeDion rear suspension, twin A-arms front, and a 315hp small block with aluminum big-valve heads. One of Duntov’s devious procedures actually produced two SSs—one “mule,” one “finished” racing car. The racing car was built with full Motorama finish, but no time left for sorting or practice. Running with the SR-2 from 1956 and some GT-class production-based Corvettes, the SS failed to finish, but was fast enough to encourage all those who helped design and build it.

Then, with prompting from GM Chairman of the Board Harlow Curtice, the Automobile Manufacturer’s Association banned the use of racing or high performance in auto advertising and the SS was dead.

4. STING RAY. Or was it? Mitchell and GM Styling were able to obtain the refurbished “mule” SS chassis. He had Larry Shinoda design a new body for it based on a very advanced production proposal(the”Q”—another victim of corporate Corvette opposition) and the Sting Ray was born. The Sting Ray, disproving the adage about there being nothing as old as last year’s racing car, remained competitive through 1960, running against Reventlow Scarabs, Jag and Corvette Listers, Maserati Birdcages, and the latest Porsches. It was a private entry and got precious little official help from Chevrolet or GM even though Bill Mitchell was a VP of the corporation. After its racing days, the Sting Ray became a show car.

5. PRODUCTION RACING. The irony is that the production Corvettes, old fashioned ladder frame, all iron engine, 1949 Chevy front suspension, iron drum brakes, solid rear axle, too much weight, too much drag (and in fairness, Rochester f.i., great close ratio Borg-Warner T-10 4-speed, Bendix Cerametallix brake lining) had kicked the Jaguar XK-120/140/150, the Mercedes 300SL Gullwing and Roadster (except for one factory cheater) the Ferrari 250GT and California Spider, thevetrace3.JPG (11764 bytes) Porsche Carrera Speedster GT–all that light alloy, all of those camshafts, all of that trick suspension—right out of any contention on US tracks from late 1957 until the Shelby Cobra muscled in late 1962. Even then the Corvette held its own. When the SCCA massaged the classes, the Corvettes regained their dominance.

6.CERV I. The Chevrolet Experimental Research Vehicle I was not a racing car. It was only a coincidence that it was built to fit all of the Indianapolis specs. Indy was just the barest possibility—Pikes Peak (where Duntov had set a record in 1956) was the real target. The run was to be made under the Firestone flag to get around the GM racing ban, but due to poor information, it was never made.

The next target was the first 180 mph lap at the new Daytona Motor Speedway. The record was held at 176+ by an Indy car. The CERV I engine was a very special (high-silicon alloy block like that used by Vega, Porsche 928 and MBz V-8 ten or twenty years later, alloy heads, ram tuning on the Rochester fuel injection, light alloy starter motor, magnesium clutch housing, etc.) 353bhp small block with well over one bhp/lb. It went 167. Duntov turned Chevy talent to further engine development and eventually a dual-turbo (TRW turbos) version of the light alloy engine was produced with 500 bhp. No record was set with this pioneering effort but a later 366 cu.in. small block produced 206 mph at GM’s Milford test track. The CERV I gave Chevy experience with mid-engined design, transaxles, high speed aerodynamics, the Reynolds 390 high-silicon light alloy block casting technique, ram tuning and the rear suspension that was later used in the production Sting Rays from 1963 through 1982.

7.CERV II. Chevy General Manager “Bunkie” Knudsen wanted to get back into racing so the CERV II was planned for the international prototype class with a 4-liter version of the small block using special 3-valve SOHC heads (run by Mickey Thompson at Indy). Titanium was to be used for hubs, connecting rods, valves, and exhaust manifolds. The car was to weigh under 1400 lbs. At the same time, an automatic racing gearbox without a power-wasting hydraulic coupling was designed. Construction was started almost at the same time Knudsen was ordered to stay out of racing. The CERV II was eventually built with an advanced 4wd unit, using two torque converters, a glued-together steel and aluminum monocoque, very wide wheels, low profile tires, and body by the team of Shinoda and Lapine again (Lapine’s last major job for Chevy before going to Europe and eventually Porsche). It finally used an injected alloy ohc 377 cu.in. V-8. The plan was now to use the CERV II as an anti-GT-40 weapon. GM management killed that, but the car was used as a research tool for a mid-sixties super-Corvette that too was killed. Never raced, the CERV II ended as a show and museum piece.

8. GRAND SPORT. When the corporate management forced Knudsen to turn off the anti-GT-40 project, he had Duntov turn to Plan B—a lightweight Corvette anti-Cobra. The idea was to build 125 GT cars lightly based on the 1963 Sting Ray production coupes. It had a new, large tube, ladder-type frame, a one-piece hand layup glassfiber one-piece body, lightweight, fabricated front suspension, and a version of the Sting Ray’s irs. The homologated weight was 1908 lbs. The engine was to be a pushrod hemi V-8 with an iron-linered light alloy block, dual plugs, ram-tuned mechanical f.i., and a displacement between 377 and 402 cu.in. And once again, the AMA ban and GM corporate policy turned off the tap, but this time only after five GS Corvettes had dribbled out. Using production-based small blocks, the GSs ran as modified cars against Coopers, Chapparals, Scarabs. In the hands of Texas-based Mecom Racing, three GSs, running 377 cu.in. aluminum block, Weber-carbureted small blocks with 485 bhp, did just what they were supposed to—ran the Cobras and Ferrari GTOs into the ground. They were competitive with the genuine prototypes and outright competition cars as well. The last two GSs were bodied as roadsters with targa-style roll bars, with the intent of running at Daytona (the lower frontal area of the roadster allowed a higher top speed). Once again, GM management came down on Knudsen and the program was scrubbed. Jim Hall (Chapparal) bought one coupe, John Mecom, two. The roadsters were eventually sold to Roger Penske, who had 427 MkIV big blocks installed. The GSs have changed hands many times since the mid-‘sixties, had other engines installed and have been modified in other ways, but all five (some say six) still exist and are very highly prized today. And yes, they were faster than the Cobras, including the Daytona Coupe.

9. MARK IV. There have been only three engines used in production Corvettes since 1953: the 235 cu.in. Blue Flame six, the small block (265, 283, 327, 350 cu.in. sizes) and the mighty Mark IV (396, 427, 454 cu.in.). The Mark IV was originally a secret weapon for NASCAR to allow Chevy to compete with big blocks from Ford and Chrysler. It had proven some of its ability in the GS and was then added to the production cars from 1965 through 1973. The ultimate version, the L88, reportedly had 560 bhp, although the factory never admitted it. It was available only with the Muncie “Rock Crusher” M22 gearbox, heavy duty suspension, heavy duty cooling, heavy duty everything. With 12.5:1 compression, optional aluminum heads, standard tri-power carburetion (the Rochester f.i. had been effectively scuttled by the marketing people who had been raising its price every year despite Rochester lowering the price to Chevy), it was for racing only. It was another anti-Cobra device, and was effective, at least in long distance racing. These were the days of the Ferrari GTO and 275GTB, 911R/S and 904 Porsches, and the Daytona Cobra. The L88-powered production-based Corvette won the GT class at Daytona and Sebring in 1966, at Sebring again in 1967, and managed 171.5mph–22mph faster than the winning GTB–down the Mulsanne straight at LeMans. Only about 500 built in three years.

10.MORE HOT ENGINES. ZL-1: an aluminum block version of the L88–slightly less power potential than the L88, significantly less weight. Basis for the 500 cu.in. McLaren Can-Am engines. A $3000 option, maybe 585bhp. Very rare. LT-1: 350 cu.in., solid lifters, 850cfm Holley, 370bhp (actually more than the 375bhp 327). LS-7: 454 cu.in., 460/465bhp, solid lifters, dual disc clutch. Catalogued, road tested, never sold. Another victim of upper management. LS-6: 454 with aluminum heads, 425bhp gross/325 net, 9.0:1 compression, cost $1220.

In 1973, Corvettes finished third overall at both Sebring and Daytona (IMSA’s first Daytona and the first international win for a Greenwood Corvette). With considerable help from John Greenwood, Chevy beat Porsche for the Trans-Am championship.

The 1984 and later Corvettes are truly new cars. The only part larger than a bolt that carried over from the 1982 car (there was no ’83) is the engine. The chassis uses a “birdcage” space frame welded up of steel pressings. Halfshafts and driveshaft are aluminum, as are the front A-arms, cylinder heads, water pump, etc. Headers are tubular. Springs are transverse fiberglass leaves front and rear. It is the only production car to actually be able to corner at over 1.0 G. The 1984 Corvette became an immediate winner in SCCA events and remains without real competition today.

Top image: 1962 CERV II (Michael Furman photograph, courtesy of RM Auctions)

---

The late Len Frank was the legendary co-host of “The Car Show”—the first and longest-running automotive broadcast program on the airwaves. Len was also a highly regarded journalist, having served in editorial roles with Motor Trend, Sports Car Graphic, Popular Mechanics, and a number of other publications. LA Car is proud to once again host “Look Down the Road – The Writings of Len Frank” within its pages. Special thanks to another long-time automotive journalist, Matt Stone, who has been serving as the curator of Len Frank’s archives since his passing in 1996 at the age of 60. During the next few months, we will be re-posting the entire collection of “Look Down the Road”, and you’ll be able to view them all in one location under the simple search term “Len Frank”. – Roy Nakano