Building the Beast

Manufacturing the Corvette ZR-1’s high-tech LT5 engine required an all-new approach

September 22, 2016
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In early 1986, initial development of the upcoming Corvette supercar’s 5.7-liter, dual-overhead-camshaft LT5 V-8 was already underway at Lotus Engineering in Hethel, England. Meanwhile, at General Motors’ Warren Tech Center in Michigan, decision makers were homing in on the best way to construct the high-tech powerplant.

Roy Midgely, Chief Engineer for 90-degree V-Engines; Russ Gee, Director of Chevrolet Powertrain Engineering and Dick Donnelly, Chevrolet Engine Manufacturing Manager, quickly dismissed using a GM engine plant for several reasons. First, these plants were already struggling to meet demand. Second, the LT5 would be a low-volume project unsuited for high-volume facilities. Third, GM’s plants could not produce the engine’s complex aluminum castings. And finally, they were not capable of achieving the necessary level of quality.

In short, the project would require an outside contractor. The team decided to target a U.S. manufacturer with which GM already had a working relationship: MerCruiser in Stillwater, Oklahoma, which had been “marine-izing” Chevy engines for decades. As a world leader in the computer-numeric-controlled (CNC) machining of complex aluminum castings, MerCruiser was a natural fit for low-volume, high-quality, high-performance engine programs. On March 20, 1986, the two corporations cut a deal to build LT5s. Just 21 months later, on December 24, 1987, the first MerCruiser-built LT5 ran on a dynamometer at the Stillwater plant.

In June of the following year, the engine debuted during a 1989 Chevy-model preview held at Riverside International Raceway in California. During an introductory Friday-evening press conference at the Riverside Convention Center, Midgley delivered a briefing on the LT5 while MerCruiser Assembly Manager Chris Allen and Chevrolet Technician Ron Opszynski assembled one of the engines at stage right. As Midgley finished, Opszynski fired the engine and let it idle. Naturally, this demonstration would become the talk of the preview season in ’88.

The next day, media reps were allowed to examine LT5 engine parts at the racetrack. I was impressed with the quality of the machining, and decided I need to visit the facility where the engine was made.

Accuracy

The following December, I toured MerCruiser’s Stillwater facility as part of a story for Road & Track. It was immediately obvious from the bright lighting, low noise level and spotlessly clean work areas that this was no typical engine plant. The LT5 area’s 21,000 square feet were split into machining and assembly. Machining operations were performed in a temperature-controlled room filled with Cincinnati Milacron T10 three-axis machining centers, a cam-bore machine, a straddle mill and other equipment. All of it operated by CNC, with a computer controlling both the cutting tool(s) and how the parts were positioned during the process.

Also from Issue 109

  • 2017 Corvette Grand Sport
  • 1969 Vintage Racer
  • Buyer's Guide: C1
  • Export Split-Window
  • Supercharged 50th Anniversary C5
  • Road-Trip Prep
  • Privately Owned C6.R
  • Racing: The Taylor Brothers
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