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Corvette ZL1
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  Chevrolet Corvette ZL1
 

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Country of origin:United States
Produced in:1969
Numbers built:Around 7
Internal name:C3
Author:Wouter Melissen
Last updated:January 14, 2013
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Click here to download printer friendly versionAlthough there was no official works racing program, privateers campaigning Corvettes did receive backdoor support to ensure Chevrolet's range topping model held its own on the track. Many of the competition components were actually readily available as a Regular Production Option (RPO), which ensured Chevrolet's anti-racing policy was not violated. When Carroll Shelby launched the big block version of the Cobra early in 1965, an altogether more exotic option was readied. Known as RPO L88, this was a very hot version of Chevrolet's own '427' big block engine.

The only major component carried over from the existing 'Mark IV' V8 was the cast-iron block, which was considered strong enough to cope with the increased forces. The stock block was fitted with an especially forged crankshaft onto which reinforced connecting rods and aluminium pistons were bolted. Combined with the bespoke aluminium heads, these competition specification pistons were good for a staggering compression ratio of 12.5:1. Also part of the package were a four-barrel Holley 850 carburettor, a very hot camshaft and a valvetrain equipped with hardened, heavy-duty components.

Despite all these upgrades and a $947.90 premium, the L88 engine was rated at 'only' 430 bhp, which was actually 5 bhp less than the standard Mark IV V8. This was done deliberately to ensure the engine would not stand out and attract too much attention. Due to the high compression, the L88 could only run on 103 octane fuel, while the other competition components did not make it particularly suited to road. Experienced racing teams knew very well how to tweak the engine for full performance, like replacing the very restrictive exhaust headers. Later tests showed that the V8 was actually capable of producing in excess of 540 bhp.

To further deter customers from acquiring the L88 for road use, it was very minimally equipped; luxuries like power windows or even a radio were simply not available. Driving the car was also far from easy due to the heavy-duty but also very rough RPO M22 'Rock Crusher' gearbox. At the very end of the L88 production run, an automatic gearbox did become available. Further complicating matters was the lack of a choke and a fan shroud, which made it prone to overheating at low speeds, particularly in traffic. On the outside, there was little to distinguish the L88 from other big-block Corvettes and there was certainly no special badge.

Although the first L88 engine ran late in 1965, the option did not become available until the spring of 1967; right at the end of the production cycle of the second generation or 'C2' Corvette. As a result only 20 Corvettes were built with the L88 engine that year. Following the launch of the restyled 'C3' Corvette in 1968, production was ramped and an additional 80 examples (Coupes and Roadsters) of the competition ready machine were built. With production now exceeding 100, this meant the engine was fully homologated for national and international events. The L88 remained an RPO through to 1969 when a further 116 examples were specified with the potent V8.

One of the first competition outings for the L88 Corvette was the 24 Hours of Le Mans in June of 1967. Driven by Bob Bondurant and Dick Guldstrand, the potent machine reached speeds of up to 171 mph but was eventually forced to retire with a broken engine. With the introduction of the C3 in 1968, true racing success came for the L88 Corvettes. In that year's SCCA A-Production class, a big-block Corvette would win eight races out of eleven attempts. The L88 Corvettes would remain successful for several more seasons, scoring outright wins on the American continent and also numerous class victories in international events.

For 1969 an even hotter RPO was added to the Corvette option book. Known as the ZL1, this included an all-aluminium version of the big block, which was also used in the popular Can-Am Challenge. Only around a dozen were built and reportedly just two were sold as the engine alone was just expensive as a complete small-block Corvette. In 1970 neither the L88 or ZL1 were back as Regular Production Options. Due to their rarity and extremely powerful, race-bred engines, these remain among the most desirable Corvette 'road' cars.

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