The LS1 engine is first member of the third generation of the GM small block V8 engine. Although touted by GM as an evolutionary development, LS1 engine shares only bore spacing dimensions with the Gen1 and Gen2 small block. The engine was first used in the 1997 C5 Corvette, followed by the Camaro and Firebird in 1998.
Displacement is 346 cubic inches. In the 1997 Corvette, this engine produced a factory-rated 345 horsepower (nearly 1hp per cubic inch) and 375 lb-ft of torque. The 1998 Camaro Z28 and Firebird Trans Am were rated 305 horsepower and 335 lb-ft of torque, but it has been repeatedly demonstrated that the actual power output was much closer to that of the Corvette. Camaro SS and Trans Am WS6 models received a 320 hp, 345 lb-ft rating, credited to ram air induction and a freer-flowing exhaust system, but dyno testing indicates that the power difference between the Z28/Trans Am and the SS/WS6 is negligible.
With emphasis on serviceability, most of the LS1's gaskets are re-usable, and an engine can be completely disassembled in just a few minutes.
The firing order of the cylinders (1-8-7-2-6-5-4-3) is different from the traditional small blocks, which increases horsepower, smooths power delivery, and improves reliability by reducing strain on the crankshaft compared to the traditional V8 firing order. The modified firing order also gives the engine a distinct exhaust note. Many enthusiasts feel that the traditional firing order results in a better sound, while others feel that the new sound has an exotic, European feel.
The LS1 abandoned the reverse-flow cooling system of its predecessor, the LT1. This is generally credited to a dispute with Evans Cooling over the technology.
Other significant changes from the previous generation:
- Coil-on-cylinder ignition
- Replacement of the troublesome OptiSpark
- Composite intake manifold
For the 2001 model year, GM introduced the LS6 engine in the Corvette Z06. A new intake manifold, revised heads, and a new camshaft profile raised rated horsepower to 385. All LS1 engines built for 2001 and later used the revised LS6 intake manifold and a different camshaft, increasing horsepower ratings by 5 hp and 5 lb-ft across the board (350hp in the Corvette, 310 in the Z28/Trans Am, and 325 in the SS/WS6). For 2002, the LS6 received a new camshaft, increasing power output to 405 hp.
The LS platform was further extended by a fourth generation of engines, including the LS2, LS7, LS3, and LS9.