The Four-Rotor Corvette Prototype Was the ‘Almost’ Mid-Engine Production Corvette
Duntov was rankled by the Wankel, but loved the Four-Rotor’s exterior style.
Famed Corvette engineer Zora Arkus-Duntov absolutely did not want to do the Wankel-rotary-engine-powered Four-Rotor Corvette project, which itself was an evolution of the mid-engine XP-882 prototype. With his retirement looming, the window of opportunity for a mid-engine Corvette was narrowing. Familiar with the Wankel engine since 1955, Duntov knew that the basic design was inefficient because of the surface-to-volume ratio in the combustion chamber. Additionally, the Chevy Vega was scheduled to be the first Wankel-powered car produced by General Motors and Duntov didn't want the Corvette to be powered by a Vega engine. But GM president at the time Ed Cole was hot on the Wankel and tactically said, "yes" to the mid-engine Corvette, but only with a Wankel in the middle. Duntov had no choice.
Duntov made the best of it and told his engine man, Gib Hufstader, "Make me a fast car!" Hufstader's solution later won a U.S. patent. The layout consisted of two separate Wankel engines, one on each side of a shaft that ran back to the bevels at the transmission output. Each engine was 90 degrees out of phase to smooth out the performance. A toothed and grooved cog belt ran the ignition, alternator, and fuel pump, while a V-belt controlled the air conditioning, power steering, and water pump. The combined size of the two engines was 585 cubic inches and was rated at 350 to 370 horsepower. Hufstader said with some development the setup could make as much as 480 horsepower. He pulled it all together in just two months. In July of 1972, Cole, with Duntov, took the completed, body-less car out on the GM Tech Center check road. Legend has it that the car hit 148 mph and was still accelerating when they had to slow down. The sound was described as an "incredible shriek!"
As development continued, Duntov eventually cornered GM vice president of design Bill Mitchell and said, "Let's put a deadline on this. The Paris show." Mitchell agreed and assigned the project to Hank Haga and Jerry Palmer. Mitchell wanted to see a break from the Kammback design, something pointed and streamlined, similar in flavor to the Mercedes-Benz record-breakers of the 1930s. Palmer recalled: "It was a very hard car to design. After my second shot Mitchell said, 'Hey, look, this is like baseball, kid—three strikes and you're out.' "
"Mitchell wanted a teardrop shape," Haga explained. "The design problem was to put together a piece of equipment that didn't have a tail 40 feet long. It started with a long nose and tail … it looked like a record car rather than a Corvette. So we did several overlays and got a fair balance between the nose and tail. We kept shortening it and that's how it evolved."
