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The Lotus-Engineered DOHC V8 Engine Is Far Different Than The Supercharged Small Block We Know Today

C4 Corvette ZR1 ZR-1 LT5 DOHC V8 Mercury Marine Lotus Engineering GM Engines

Available now is the first production LT5 V8 engine that was originally produced by Mercury Marine for use in the C4 Corvette ZR-1. Seriously, engine unit number “0000” is available for sale through Automation Classics in Troy, New York. Hand-written notes on the outside of the crate and along with included paperwork prove the engine’s provenance. The crate was opened for photos, but the lag bolts holding the engine in place have not been removed since it was shipped out by Mercury Marine all those years ago.

During 1986 General Motors acquired a majority stake in the famed UK engineering and performance car firm, Group Lotus. Shortly after the union was made, Corvette engineers enlisted Lotus to help transform the C4 Corvette into the world’s fastest production car capable of taking on the best from European stalwarts Ferrari and Porsche.

For that, they would need a new motor.

With input from their colleagues in Detroit, Lotus Engineering began design work on an all new engine that would fit within the same footprint as the contemporary L98 found under the hood of the C4. The result was an aluminum-block 5.7-liter V8 with the same bore centers as the L98, but with four overhead camshafts and 32 valves instead of the typical cam-in-block setup. It was dubbed the LT5, and it was spectacular.

C4 Corvette ZR1 ZR-1 LT5 DOHC V8 Mercury Marine Lotus Engineering GM Engines
Image via Automation Classics.

There was a forged crankshaft, lightweight pistons and connecting rods, and a compression ratio of 11:1. The result was a dazzling 375 hp at 6,000 RPM and 370 lb-ft of torque at 4,800 RPM. There was even a trick intake system that widened the power band by shutting down 8 of the 16 intake runners and fuel injectors when the engine was at part-throttle.

But now General Motors had a new problem. At the time, the company had little to no knowledge of what it took to build small-batch, high-performance, all-aluminum engines. Team Corvette turned to another outside source: Mercury Marine’s MerCruiser division due to their experience producing aluminum outboard motors.

MerCruiser chunked out a special section of their Stillwater, Oklahoma facility where the LT5 was hand-built to extremely tight tolerance in absolute clean-room conditions. The engine was built so well it actually became the first GM badged motor to receive the automaker’s most demanding quality certification — GP3 Level 1. It also happened to set seven international and world records for speed and endurance in a factory-stock production car.

It’s strongly believed this engine is the very first production based C4 Corvette LT5 engine to ship from MerCruiser. Per the Corvette Action Center, Brett Shank of Automotion Classics acquired the engine from the the estate of Rick Kirk, the long time owner of RK Machine in Ripley, Oklahoma. RK did much of the early LT5 prototype work under contract to Mercury Marine and Lotus. All this could be yours for just $12,900.

– By Michael Accardi

C4 Corvette ZR1 ZR-1 LT5 DOHC V8 Mercury Marine Lotus Engineering GM Engines
Image via Chevrolet

Written by MC&T Staff

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  1. No experience with small batch aluminum V8 engine the Buick 215 that became the rover V8 used till the 2000s the aluminum corvette motors of the 60s no experience do some decent research before you write things. Do you talk out of your butt you look up simple facts before you write or do you just base things on how you feel about gm

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