The "LS" engine designation here refers to the 3rd and 4th generation Chevrolet small-block V8 engine and should not be confused with the LS3 402 cubic in engine and LS5/LS6 454 cubic inch engines of the 70s. or L34/L35/L78 engines of the 60s and 70s. The 'new' LS engines are very different from the 1st and 2nd generation Chevrolet small-block V8 engine originally released in 1954 for the 1955 model year.

Many variations of the "LS" engine and often referred to as "LSx" (lower case "x") for one of the many regular production option (RPO) code variations of the engine. Note that the "LS" designations of these Gen III and Gen IV engines should not be confused with the "LS" engines of Chevrolet and other GM Division engines of prior years.

General Synopsis

Gen III - 1997-2007

The GEN III engine blocks were cast aluminum for car applications and iron for most truck applications with exceptions for the Chevrolet Trailblazer SS, Chevrolet SSR, and a limited run of Chevrolet/GMC Extended Cab Standard Box Trucks. The new LS engines use a coil-near-plug style ignition to replace the convectional distributor ignition used previously. The firing order changed from 1-8-4-3-6-5-7-2 to 1-8-7-2-6-5-4-3.

LS1 - Introduced in the 1997 Corvette and rated at 345 hp and used through the 2004 Corvette model year. The LS1 engine was used in several other GM offerings such as the 1998-2002 Camaro and Firebird, 2004 Pontiac GTO and GM of Australia's Holdens. The engine size is 5.7 L or 350 cubic inches.

LS6 - The same size and design as the LS1 but with a higher horsepower rating, 405 hp. This engine was used in the 2001-2004 Corvette Z06 and 2004-2005 Cadillac CTS V-series.

Gen IV - 2005-2020

The Gen IV engines have provisions for up to 7.4 L, or 454 cubic inches, and up to 776 hp. The Gen IV is designed with displacement on demand that allows every other cylinder in the firing order to be deactivated

LS2 - The LS2 was the new base Corvette engine for 2005 and was rated at 400 hp with a slight increase in displacement up to 6.0 L or 365 cubic inches.

LS7 - The LS7 boasted a 7 L or 427 cubic inch displacement and was rated at 505 hp. The LS7 was hand-built by the General Motors Performance Build Center. Most LS7s were installed in the 2006 and later Corvette Z06 and were also sold by GM as a crate engine.

LS3 - Introduced for the base engine in the Corvette for 2008 with a 430 hp rating. An updated version of the LS2 with a slightly larger cylinder bore that brought the displacement up to 6.2 L or 376 cubic inches.

LS9 - A supercharged version of the LS3 rated at 638 hp and used in the 2009-2013 Corvette ZR1.

See Wikipedia for more detailed information.