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The LT1 and L99 are both from the General Motors (GM) LT line of small-block V-8 engines. The LT1 was first introduced in 1992. General Motors wanted output similar to the high-performance LT engine of the 1970s. The LT line was first introduced in the GM flagship Corvette.
LT1
The LT1 is a 5.7-liter (350-cubic-inch) engine and has a two-valve pushrod design. The LT1 has a "reverse flow cooling" system that enables the cylinder heads to be cooled first. This results in keeping cylinder temperature lower and letting the engine run at a high compression. The engine has a cast-iron block and aluminum or cast-iron heads, depending on which car it is in. The Corvette LT1s have four-bolt main caps, and the other cars that used the LT1 had two-bolt main caps. The engine produces around 300 horsepower.
L99
The L99 is a 4.3-liter (263-cubic-inch) engine. The stroke was reduced from the 5.7 liters by 3 inches. The engine was first introduced in 1994 and available in the Chevy Caprice. It is almost the same as the LT1 except for the bore of 3.736 inches and the stroke. Also like the LT1, the L99 features a sequential fuel injection system and reverse-flow cooling as well as an optical ignition pickup. The output on the L99 is 200 or 245 horsepower. It has better fuel economy but less power.
Similarities and Differences
The engines are virtually identical except for the bore and stroke. The L99 also uses pistons from the Vortec 5000. However, other than that the two engines are identical. The L99 was introduced as an option for cars that required better fuel economy.
Cars
The cars that used the LT1 were the Corvette C4, Chevrolet Camaro, Pontiac Firebird, Buick Roadmaster, Chevrolet Caprice, Chevrolet Impala and Cadillac Fleetwood. The only car to use the L99 was the Chevrolet Caprice.
