1990-1992 C4 Chevrolet Corvette ZR1: LT5 Engine, Pricing, and Performance
The LT5 motor, which had very little in common with the previous LT, was a next generation small block Chevrolet engine used only in Corvettes. It had a new block cylinder head, intake manifold, timing cover, water pump, and "opti-spark" distributor. The block was aluminum and the engine sported 32-valve cylinder heads with double-overhead camshafts. The bell-pattern bell housing and the engine mounts were the same as the previous small blocks, allowing for easy replacement of an old engine with a new one.
Specs for the engine in the 1990 through 1992 ZR1 Corvettes are: 349 cubic inch (5.7 L) displacement, 375 horsepower (280 kW) with 370 lb. ft. (502 Nm) of torque, and bore and stroke was 3.9 inches (99 mm) to 3.66 inches (93 mm). In the 1993 through 1995, the engine produced 405 hp (302 kW) with 385 lb. ft. (522 Nm) of torque due to better engine porting and changes in timing. Unique to this generation of small blocks also was the "reverse" cooling system. This system cooled the cylinder heads first, then the cylinders. The result was cooler heads, which produced the ability to achieve a greater spark advance and a higher compression ratio. This in turn yielded more power. The LT5 motors were built by hand in Stillwater, Oklahoma by the Mercury Marine Company.