Genetically modified: Driving the original Corvette Sting Ray

Chevrolet’s first-ever factory involvement in racing had taken place when ex-works Mercedes driver John Fitch oversaw a team of three road car-based Corvettes at the 1956 Sebring 12 Hours. As Duntov had predicted, they were easily outclassed by the specialised Jaguar D-types and Italian exotica. But GM president Ed Cole was excited by the project and by mid-year had handed Duntov his ideal remit: to build a bespoke Chevrolet sports-racer.

In a walled-off corner of the Chevrolet factory, the steel tubular spaceframe SS chassis and body were designed, complete with a fuel-injected 283 cubic inch (that’s 4.63 litres to us Limeys) V8. The first chassis, fitted with a makeshift fibreglass body, became known as the SS Mule and stacked up over 2000 miles of testing in the run-up to Sebring in ’57. The team, meanwhile, were desperately putting the finishing touches to the magnesium bodywork of the race car.

The day before the event, no less than Juan Manuel Fangio and Stirling Moss tried out the Mule, and both came away impressed – indeed, ‘The Maestro’ lopped 2sec off his fastest lap from the previous year. But the late arrival of the race car put Fangio off, leaving Fitch to share it with Piero Taruffi. The American ran as high as sixth in the early stages before a catalogue of problems meant an early exit.

Three entries were filed for Le Mans, but in May Duntov was told to close down his racing department. The Automobile Manufacturers Association had made a proclamation that road safety was being jeopardised because motor sport encouraged high speeds, and General Motors leapt on the bandwagon banning racing. The SS was over as quickly as it had begun – but it had a knock-on effect.

A racing fan since the pre-war days, Mitchell used the inspiration of the SS to design a clay model of a concept shape for a road-going car called the Q-Corvette. He aspired to have this replace the boxy 1950s shape of the ‘Vette, and came up with the notion of turning it into practice via a racer paid for out of his own pocket. Against Duntov’s wishes, Mitchell used his own newly acquired political clout to commandeer the SS Mule chassis in 1958.

What really interested Mitchell was the shape that would clothe the chassis. His aim was for his department to produce a body akin to that of a shark, but the result of his and Larry Shimoda’s after-hours project was more reminiscent of another sea-going predator and it was soon tagged the Sting Ray.

Aware of the trend to enable easy access to the internals, Mitchell designed the two body sections to be hinged fore and aft to open in a clam fashion. Now, before I step aboard, we unfasten the silver panels (which are, crucially, still the originals) to inspect the Sting Ray’s innards.

The underside of such beauty is less aesthetically pleasing: the three-skin fibreglass body, which is supported by balsa wood (!) cross members, is finished in matt black enamel. The spaceframe chassis looks crude in comparison to rivals of the day — the delicate intricacy of a Birdcage or the subtlety of a Porsche RSK. But it matters little, for the eye is drawn immediately to the gleaming brute ahead of the cockpit.

Nowadays the engine bay holds a 327 cubic inch V8, as opposed to the 283 that pumped out 280bhp at 6200rpm for the Sting Ray’s racing career in 1959-60. (On the car’s retirement Mitchell fitted a 7-litre 427 mill for his personal road-going pleasure!) Mitchell experimented with aluminium heads, but the same Rochester fuel injection system from the SS Mule was retained for the Sting Ray along with much of the rest of the driveline and de Dion rear suspension.

Disc brakes were fitted after the car’s racing career was over, and the huge ducts that lead air to the inboard rear stoppers speak volumes about the difficulties Thompson faced while racing the car with its outdated drums.

In the cockpit the only link to the SS is the three-spoke steering wheel, which is removable for easy access. It’s spartan inside, but the upright seating position is comfortable and gives an easy eyeline to the four gauges in front – oil pressure, oil and water temperature, and the tachometer to the right. The speedometer, an addition to comply with road-going specs for Mitchell’s later enjoyment, is completely obscured by the wheel. Also effectively redundant are the side mirrors, the racer’s central fitting being the main aid. The two-stage ignition sits to the right and, with a little help of the throttle, at the second try, we have lift off.

There is not so much a rumble as a series of angry V8 thuds. There is no staccato effect – it’s more as if each individual combustion can be clearly deciphered from the next, the note authoritative and menacing, even as it idles lazily at little more 1000rpm. And boy, do your eardrums get with the beat.

In unsilenced form, the single chrome-plated ‘drainpipes’ that unfurl along each flank blow puffs of dust across the ground up to 10 feet away. The rhythmic explosions reverberate along your spine. Even when you’re standing half a mile away, you can hear every blip. But now, I’m up close and personal – and intimidated.

Once onto Millbrook Proving Ground’s Hill Course, however, the V8 proves amiable enough – as does the whole package. The clutch is relatively heavy, but the small, wooden-headed gearlever slides readily and smoothly through its ‘five on the floor’. The steering is light and responsive and the engine, once it’s burbling along, is as unfussy as you’d expect, the torque so great that even on the many slow corners gear selection is far from critical.

These twists and turns are even rather apt, reminiscent of the tight road courses on which Thompson campaigned the Sting Ray in the SCCA national events. But, as I am to keep it below 5000rpm, there is no opportunity to even try to test the limits in the style of Dr Dick, who was famed for wringing the Sting Ray’s neck in crowd-pleasing fashion.

“It was one of the favourite cars of my career,” relates Thompson now. “For me, and most others, its beauty transcended everything. But it had a light feeling and always handled well. I was always hoping it would be developed to its full potential, but there were fundamental problems that were never addressed.”

The key problem, from that very first race at Marlboro, were the brakes, always the Achilles heel of the Corvette. Under Duntov’s watchful eye that day, Thompson’s early lead was soon lost when he suffered a spin, because by the halfway stage he had “literally no brakes left at all”. It was the same story throughout the rest of the season – quick in the early stages, fading as the race went on. Also, while the bodywork was certainly aerodynamic, allowing a top speed of 155mph with racing gearing, at Elkhart Lake the car revealed an alarming tendency to lift at high speed. This was solved by raising the rear coil springs to produce a more forward rake.

But a whole ream of further changes was required, and over the winter of 1959-60 Mitchell’s team set to it. The relative backwardness of GM’s motor sport innovations meant that disc brakes, a standard item for the Sting Ray’s racing rivals, were simply not available. So Mitchell introduced a Hydrovac power-assist system to the heavy twin-servo drum brakes. Weight was a contributing factor to the braking deficiency and the three-skin body, painted silver, was fitted to bring the weight down to 900kg, closer to the opposition.

The other major hindrance was that there was no limited-slip diff, and Thompson often wasted time waiting for the back wheels to stop spinning as the V8 kicked in. The compromise that winter was to weld together the differential gears to produce a locked rear end. But all in all, the changes had minimal effect.

“There wasn’t a dramatic difference in 1960,” says Thompson. “Now the brakes ran out two-thirds instead of halfway through. It looked dramatic because I always had to be sideways through the corners to slow the thing down. And the locked diff, while reducing wheelspin, simply introduced chronic understeer.

“If we just could have developed the engine, it could easily have found 50hp more. The potential was never realised: if we’d had a limited-slip diff and disc brakes we could have matched all the others.”

Nevertheless, 1960 proved a better year, and Thompson regularly beat Maserati T61s and Lister-Jaguars as he notched up four podium finishes in nine races, the highlight of which were two terrific battles at Elkhart and Meadowvale with Augie Pabst’s Scarab. The consolation for no overall wins was that, against minimal opposition, Thompson wrapped a class title in the C-modified section.

In the bigger scheme of things, what perhaps mattered more to Mitchell than the results was the enthusiastic reaction that the Sting Ray generated from the general public – and even from some elements of the GM hierarchy. In its retirement the unofficial racing creation suddenly became acceptable and was paraded across the country at motor shows as a Chevrolet concept car.

And so, as I roll to a halt and turn Sting Ray’s clattering soundtrack into polite silence, I am aware that it was not its performance that was essential, it was those beautiful silver panels that had won over friends in high places. By 1963, Mitchell had the first Sting Ray Corvette road cars in production – much to Duntov’s chagrin. A firm believer in the mid- or rear-engined concept, Zora had wanted the Corvette to head in that direction. But the Sting Ray had won the day and moulded the Corvette’s front-engined look forever.

There has never been a mass-produced rear-engined American sports car since. Now that’s a lasting impact.

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Technical specification
Engine
Type (circa 1960): V8, aluminium head and cast-iron block

Capacity:4637cc

Compression: 11:1

Max power: 280bhp @ 6200rpm

Carburation: Rochester fuel injection

Drivetrain
Gearbox: 5-speed

Chassis
Type: steel tubular spaceframe

Weight 900kg

Suspension (f): independent, wishbones, coil-springs/dampers, anti-roll bar

Suspension (r): de Dion rear axle, wishbones, coil-springs/dampers, anti-roll bar

Running Gear

Brakes: inboard, twin-servo drums, Hydrovac power assist