What do you do if your 535ci, nitrous-injected Corvette just isn’t fast enough? Well, if it’s 1978 and you’re corporate jet entrepreneur Herb Orlowitz, you call your friend Vince Granatelli (son of “Mr. 500” Andy Granatelli) and ask him to build something “really fast.”
As Peter Frey told the story in the Nov. 1979 issue of Motor Trend, Granatelli at first offered Orlowitz one of the turbine-powered Lotus 56s that ran the Indy 500 in 1968, the Graham Hill car that had been recently restored. But Orlowitz wanted something street legal, so Granatelli stepped up to the challenge.
A Corvette was deemed the most suitable platform for such a beast because “its high performance capabilities were a known factor,” wrote Frey. Also, the car’s long nose would accommodate the Pratt and Whitney ST6B turbine engine, which was nearly three times as long as a conventional V-8.
Granatelli began the process with a brand-new 1978 Vette. He described the modifications as “straightforward,” but they weren’t easy. To make room for the turbine he removed the stock front clip and replaced it with a bare fiberglass shell, under which he built a new subframe. Granatelli also constructed “a flat box that covers almost the entire underside of the car” said Frey, to handle the huge amount of airflow coming from the engine. “If eight turbocharged Indy Cosworth motors were run at top speed, they would produce the same amount of exhaust gas flow as the turbine,” Granatelli told Frey.
Under normal conditions, the ST6B would turn 37,500 rpm. To get that down to a manageable number for the car, a Pratt and Whitney reduction gearbox was attached to the back of the engine, bringing the revs to 6,230. The engine’s 880 horsepower and 1,161 lb-ft of torque were then routed through a modified TH400 automatic transmission to a strengthened driveshaft and a 3.08 rearend.
Even with the gear reduction, the Vette would accelerate to 60 mph at idle. So “massive, ventilated, NASCAR-style disc brakes” were mounted at all four corners, and keeping the Vette within urban speed limits meant riding the brake pedal. The throttle was used only on the highway and the racetrack.
Speaking of which, Frey noted that getting acceleration data took some doing. Their first attempts to launch the car broke a retaining clip in the driveshaft U-joint. After repairs, a second try “with a more restrained starting procedure” netted them a 12.0-second e.t. at 111 mph.
“Our best run, which achieved a delicate balance of acceleration and wheelspin, left a pair of parallel streaks down the racetrack for 1,270 feet, with darker patches that indicated the transmission shifts,” wrote Frey. “Though the numbers are impressive, they cannot convey the tremendous rush of sensations that occurs when the car is at full throttle. There is almost no vibration from the engine, but there is a waterfall of noise, and acceleration that literally pinned us back in the seats.” MT’s data loggers recorded a 0-60 time of 3.6 seconds—Granatelli would later report a 2.5-second 60-mph sprint—and Frey said the Vette topped out at 180 mph.
Parnelli Jones had a chance to drive the Turbine Corvette on Ontario Motor Speedway’s 2.5-mile oval. He called the car “fantastic!”
PJ told Frey, “Straight-line stability was good, and it handled through the turns pretty much like any Corvette. I’ve raced at this track in NASCAR-type stock cars, and with their racing tires and more highly modified suspensions, they turn better lap times, but they don’t accelerate as fast as the Corvette, and they don’t come out of the corners anywhere near as quick. The torque of this engine is tremendous.”
In the summer of 1979, Petersen Publishing’s Bob D’Olivo photographed the Turbine Corvette with the Hill-driven Lotus 56. Austin, Texas, collector Milton Verret reportedly bought the Vette in 1982 for more than $500,000, and he would come to own the Lotus as well. Both were offered at the Barrett-Jackson Scottsdale auction in 2015, but neither met its reserve.
Photography by Bob D'Olivo, Petersen Archives