The Real McCoy

Also from Issue 58

  • Lingenfelter Supercharged C6
  • Interview: Ken Lingenfelter
  • Road trip: 2010 Grand Sport coupe
  • 1996 LT4 coupe
  • Market Report: C4
  • Special-order 1967 big blocks
  • Racing: GT2-class C6.R race car
  • How To: C5 headlight gear replacement
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Realizing that he needed a dramatic achievement to let people know about the Corvette’s new personality, Duntov hit on the idea of a high-speed record run. A figure of 150 mph, he figured, should be within the new car’s reach. Chevrolet boss Ed Cole gave the green light to the scheme.

Duntov used a V8-engined ’54-bodied prototype for initial tests on the banked track at GM’s Milford Proving Grounds to find out what he’d have to do to hit 150 at Daytona Beach, where national attention was focused on high-speed runs in the 1950s. With Jim Premo’s help, he fitted a racing windshield and a full belly pan. Aerodynamic mods in place, Duntov calculated that he needed about an additional 30 horsepower from the 195-bhp mill to hit the mark.

Drawing on his considerable experience with pushrod engines, Duntov designed a new camshaft. Though it had less lift than the factory high-performance cam, it provided a fuller valve-opening curve. Jerry Burton quoted famed racing mechanic Smokey Yunick as saying, “It was just a little better than what we’d call a ‘three-quarter’ cam. It was extremely durable and increased performance without totally destroying the bottom end…you could drive it on the street.”

Because Duntov’s camshaft was unorthodox by GM’s standards, some time elapsed before he was able to get it approved and have a sample sent to GM’s Phoenix Proving Grounds for testing. He and the test mule, now fitted with ’56 bodywork, arrived there in December 1955. The car had been further streamlined with a tonneau cover and a finned headrest. At the track, Duntov blocked off as much of the grille opening as possible, retaining just enough cooling air for the engine to survive the speed runs.

With the new cam installed, the engine ran easily to 6,500 rpm without valve bounce, and powered the Corvette to 163 mph at 6,300 rpm with 3.27:1 rear-axle gears. This, Arkus-Duntov felt, should translate into at least 150 mph on the sand in Florida.

The Chevy crew came to Daytona Beach in late December, but before the record run could commence, they had to wait for the conditions to be just right. “The sand must be a little wet,” Duntov said, “hard-packed, with no tongs of tidewater reaching in, for once you start you cannot deviate.” The stay stretched into January before the combination of wind and sand was acceptable. Under the watchful eye of NASCAR, Duntov climbed into the Corvette, with its side-bolstered driver’s seat and dash cluttered with extra test dials, and set off down the beach. The wind cooperated but the sand was only fair, allowing the tires to slip as much as five percent. Yet Duntov clocked a two-way average speed of 150.583 mph—an impressive accomplishment for a stock-bodied sports car.

Ostensibly, the engine was stock, too. Though it wasn’t actually fitted to any standard-production ’56 Corvette engines, the Duntov cam, as it came to be known, was officially an option in 1956. Dynamometer tests showed that its fitment resulted in 240 horsepower at 5,800 rpm, with a very fat power curve from 5,000 to 6,000 rpm. Maximum torque was 265 lbs-ft at 4,400 rpm.

Though the Daytona Beach speed run was a savvy public-relations stunt, simply getting the redesigned Corvette in the hands of journalists generated plenty of positive ink. The standard manual-gearbox 1956 Corvette staggered road testers with its acceleration, including yours truly. In Sports Cars Illustrated, I wrote that “as second gear takes over from first at around sixty and keeps the seat in your back ’til over a hundred, you learn what this car was made for.” I measured a top speed of 119 mph and a zero to 60 acceleration time of 7.5 seconds.

I said of its handling, “Once the wheel has been set for a bend, and the car has assumed an initial roll angle, the steering and throttle response are fast and consistent enough to allow very precise control.” I summed up by saying, “The Corvette as it stands is fully as much a dual-purpose machine as the stock Jaguar, Triumph or Austin-Healey.”

Chevrolet’s ’56 Corvette pricing also helped its image. The base figure was $3,120, an increase of just $211 over the ’55 V8-engined roadster. The result was a dramatic turnaround in sales, from a miserable 700 in ’55 to 3,467 in ’56.

Nineteen fifty-six brought the Corvette a long step forward. From a car that GM brass had rejected, it had been transformed into a package fit for princes and presidents. And Cole, Duntov and company had even more in store for 1957.

The text of this article was adapted exclusively for Corvette Magazine from Corvette: America’s Star-Spangled Sports Car by Karl Ludvigsen. He is currently updating this book for reissue by Bentley Publishers.

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