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How to Identify GM Gen III Engines

GM Generation III small block engines, also known as LS1s, made their debut in the 1997 Corvette. According to "Engine Builder" magazine, Generation IIIs replaced the LT1 series. They have a smaller block, are lighter in construction and generate more horsepower than LT1s. Identifying Generation III engines is similar to other GM engines; begin visually, then locate the engine block casting number to be thorough. Although the LS1 identifies the engine family, it actually consisted of the LS 1 through 7, the L89 and C33. Truck versions of the Generation III were called "Vortec."

Instructions

1

Determine if the year and make of the vehicle are possible Generation III candidates. According to LS1 Engine, Generation III engines were used in 1997 to 2004 Corvettes, 1998 to 2004 Camaro SS and Z28 models, 1998 to 2002 Pontiac Firebirds, the 2004 Pontiac GTO and numerous GM Truck, van and SUV applications.

2

Inspect the engine compartment. GM often put identifying decals and tags on the engine itself or in the compartment area. These may indicate the use of a Generation III engine. Also try to determine if the block is aluminum or cast-iron. According to "Hot Rod" magazine, most automobile LS1s were aluminum, while truck versions were cast-iron. Aluminum blocks will have a smooth finish as opposed to the rough grain of cast-iron.

3

Locate the casting number on the engine block. "Hot Rod" places it on the drivers side, just below the cylinder head. It is an eight-digit number.

4

Decode the casting number by comparing it to a casting number listing, similar to the one found on Fastnuf (see Resources). This listing will give the specifics of the engine in question when matched to the casting number.

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