Duntov’s Stealth Fighters – Part 1
Two of the Corvettes that established the racing reputation of Chevrolet’s sports car meet for the first time in a special exhibit at Revs Institute, opening April 6th. The Miles Collier Collection’s 1963 Corvette Grand Sport will be displayed opposite the unique 1957 Corvette SS on loan from the Indianapolis Motor Speedway Museum. Both flaunt the sheer exuberance that has made the Corvette a car apart.
by Karl Ludvigsen
Tremendous racing success not only in America but also around the world made Chevrolet’s Corvette one of the most respected sports cars on the planet. This was not the work of a moment. The Corvette’s racing career began near the middle of the last century after a white-haired Russian engineer with a thick accent joined the staff of Chevrolet Engineering. Zora Arkus-Duntov made the Corvette his own project, indeed his whole life.
Although Duntov was a racing enthusiast who had driven in competition, he was a firm believer in building special cars for racing instead of modifying production cars. He believed that this was the best approach for Chevrolet and its Corvette. That’s why Zora was not much involved with Chevy’s spontaneous decision to race stock Corvettes at Sebring in 1956. “I was not the driving force in ‘Let’s Go Racing,’” he said. “I was reluctantly pushed into it.”
Having seen his Corvettes struggle against the fine-tuned racing machinery of the Europeans at Sebring in March of 1956, Chevrolet general manager Ed Cole came around to Zora’s argument that special racing Corvettes were needed. But his preoccupation with other problems in GM’s largest division made Cole hesitate to bless such an initiative. However he green-lighted it after styling chief Harley Earl put him on the spot by threatening to restyle and re-engine a D-Type Jaguar as a Corvette for racing.
In July of 1956 a clay model of a sports car on a 90-inch wheelbase—the same as the D-Type Jaguar—took shape in the Chevrolet Studio at Styling, under the direction of Clare MacKichan. Its rounded contours, he recalled, were influenced by those of the D-Type, much-admired among his stylists. One of them was the talented Bob Cadaret, who led work on the racer-to-be.
Created under Styling Staff’s XP-64 designation, by October the racer’s styling development was essentially final. Its teardrop-shaped headrest concealed a strong circular rollover bar while rear wheelhouses were handsomely semi-enclosed. Its final wheelbase was 92 inches with 51.5-inch tracks.
The SS represented the styling of the original 1953 Corvette carried to its most glamorous and indeed sexy extreme. It was the ultimate expression of the Harley Earl Corvette era. A machine of great individuality and character, the XP-64 would be dubbed the Corvette SS, for Super Sport.
In his design of the SS’s chassis Zora Duntov had to dance to Harley Earl’s tune, said stylist Bob Cumberford: “We kept feeding Duntov body drawings and he had to fit everything inside them, rather than us clothing his chassis.” Earl’s dominant position arose from the fact that in an agreement with Chevrolet, Styling Staff was paying for the complete fabrication of the Corvette SS body. This included its skin of exotic magnesium.
Walled off by curtains and unpainted plywood sheets in a corner of the Chevrolet Engineering Center, Zora Arkus-Duntov created what would become known later as a “skunk works”. With desks and drafting tables next to mockups, trestles and surface plates, Zora worked around the clock with his hand-picked crew toward the almost-impossible goal of designing and building raceworthy cars for Sebring in 1957. Masterful fabrication work in the prototype shops of Chevrolet and Styling followed their drawings.
With time at a premium the designers followed the principle of the 300SL’s multi-tubular steel space frame, adapting it to the SS’s unique design. Suspension was parallel-wishbone in front and de Dion at the rear, the latter thought best for Le Mans—which was Chevrolet’s ultimate goal. Coil springs wrapped around tubular shocks at all four corners. Knowing there was no hope of proving a suitable in-house disc brake in time for Sebring, the Chevy men designed drum brakes for the SS. Mounted inboard at the rear, the brakes had vacuum boosters intended to give an anti-lock effect.
Use of aluminum and magnesium kept the Corvette SS light. With its 450-pound modified V-8, producing 307 bhp at 6,400 rpm with fuel injection, it scaled 1,850 pounds dry, 100 pounds less than Jaguar’s D-Type. Needing a test vehicle, Zora managed to sneak enough duplicate SS pieces through the GM workshops to make a running automobile out of a chassis that had been described to his management as an “assembly mockup”.
Both the SS and its ugly-looking test “Mule” were taken to Sebring for the 12-hour race on March 23, 1957. Nominated drivers were John Fitch, a Mercedes-Benz team member in 1955 and still a top driver, and Piero Taruffi, a silver-haired Italian racer with engineering skills that would be beneficial to the untried SS. Also piloting the Mule in practice were Briton Stirling Moss and Argentina’s Juan Fangio, reigning world champion. Fangio turned the second-fastest lap of Friday practice at 3:27.2, quicker than the fastest 1956 race lap of 3:29.7. It remained one of the best times set in the 1957 practice session. And the race SS was 150 pounds lighter.
Completely untried, the racing SS revealed two major faults. Its sweeping exhaust manifolds combined with the magnesium body to create oven-like cockpit conditions. Also the vacuum-boosted brakes were locking the wheels unpredictably. “I felt that we had somehow been cheated,” John Fitch recalled, “that if we had only been allowed another month the bugs would have been ironed out of the SS. Now with its malfunctioning brakes and many non-race-tested components I was very much afraid of failure—in fact, it was almost a certainty.”
The SS completed only 23 laps, punctuated by pit stops for flat-spotted tires, coil trouble and failing rear-suspension bushings. Taruffi pronounced the final verdict to Fitch: “To go on is without purpose.” And to Cole: “Withdraw the car.” Although its Mule version became the successful Stingray sports-racer of 1959-60, the SS never raced again. Before being gifted to the Indianapolis Motor Speedway Museum, which has kindly loaned it for this historic exhibit, it lapped GM’s circular track at Phoenix at 183 mph.
The Corvette SS was brought to a screeching halt—to use a favorite Duntov expression—after Sebring by GM’s acquiescence to a spring 1957 agreement among America’s auto makers to cease participation in racing and in the publicizing of racing successes. That ban remained in place in late 1962 when the sensational new Corvette Sting Ray first raced at Riverside in California.
To be continued in next week’s feature story