Tour the C4 Corvette ZR-1 LT5 Engine Assembly Plant

Back when the C4 ZR-1 debuted, the DOHC LT5 was also pushing the boundaries of performance.

More than enough attention is currently being given to the new C7 Corvette ZR1, and rightly so, but it’s worth a rewind and taking a look back at the roots of an equally impressive ZR-1 — the one with the hyphen in the name. It’s no secret that GM outsourced assembly of the C4 ZR-1’s LT5 to Mercury Marine, but the reasons for the move are quite interesting.

With only a few thousand motors needing assembly, GM felt a retooling of their facilities was somewhat trivial. Mercury Marine had a long history of building quality engines, and were very proficient in aluminum engine components, making a perfect partnership for the all-aluminum LT5. As such, engine components would be sent to their Oklahoma plant to be assembled.

Much more than simple assembly was completed by Mercury Marine, though, as they also handled nearly all of the machining work required prior to assembly. Precision machining and temperature-controlled rooms were critical to the manufacturing process of the LT5 due to aluminum’s changing shape and size with various temperatures.

Afterward, components would be mostly hand-assembled, with tolerances checked several times throughout assembly. Most tolerances were measured to within a few microns, and the results spoke for themselves. Output was 375 horsepower, and GM quickly set and maintained seven international speed records using that engine. We wouldn’t be surprised if they end up doing the same with the new ZR1.

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