1993 was the 40th anniversary of Corvette. The ZR-1, however, was conceived in 1986 with the objective of meeting or exceeding the performance of the best European sports cars available. The Lotus Group in England was enlisted to aid in the development of the overhead cam engine design. The LT5 engine was manufactured by Mercury Marine in Stillwater, Oklahoma. Four years in development, the 32-valve dual-overhead cam 350 cubic-inch V-8 engine developed 375 horsepower. Several records were set but most remembered was the 24 hour endurance run where this engine powered the car to 175.9 mph. The ZR-1 nameplate was retired in 1995.