L33 Engine

Specifiactions

The GM L33 engine is a 5.3-liter (325 cubic inch) Gen IV Vortec V8 engine produced between 2005 and 2007, primarily installed in Chevrolet Silverado and GMC Sierra half-ton trucks. It features a lightweight all-aluminum block and aluminum cylinder heads, making it significantly lighter than iron-block 5.3 engines while maintaining excellent durability. The engine has a 3.78-inch bore and 3.62-inch stroke, along with a relatively high 9.9:1 compression ratio achieved through flat-top pistons, which improves efficiency and throttle response. The L33 engine produces approximately 310 horsepower at 5,200 rpm and 335 lb-ft of torque at 4,000 rpm, supported by a hydraulic roller camshaft, sequential fuel injection, and coil-near-plug ignition. 

Unlike many other Gen IV LS-based truck engines, the L33 does not use Active Fuel Management (AFM), which contributes to its reputation for reliability and makes it especially attractive for performance upgrades and engine swaps. Additional features include a drive-by-wire throttle body, a 58x crankshaft reluctor, and compatibility with modern GM engine management systems, all of which help make the L33 a highly sought-after LS-family engine for both street and performance applications.  

Engine Variants

LM7

The GM LM7 is a 5.3-liter (325 cubic inch) iron-block Vortec V8 produced from 1999 to 2007 and widely used in Chevrolet and GMC full-size trucks and SUVs. It features a 3.78-inch bore and 3.62-inch stroke with aluminum cylinder heads and a compression ratio of approximately 9.5:1 achieved through dished pistons. The LM7 uses an OHV valvetrain with a hydraulic roller camshaft, sequential fuel injection, and coil-near-plug ignition. Output ranges from about 285 to 295 horsepower at 5,200 rpm and 325 to 335 lb-ft of torque at 4,000 rpm.

L59

The L59 is the flex-fuel variant of the LM7, produced between 2002 and 2007 for E85-capable Chevrolet and GMC trucks. It shares the same iron block, aluminum heads, 3.78-inch bore, and 3.62-inch stroke as the LM7, but has a slightly lower compression ratio of around 9.4:1 to accommodate ethanol fuel. The engine uses dished pistons, a hydraulic roller camshaft, sequential fuel injection, and coil-near-plug ignition with drive-by-wire throttle control.

LM4

The LM4 is an early aluminum-block 5.3-liter V8 produced from 2003 to 2004 and used in vehicles such as the Chevrolet SSR and extended-length GMT360 SUVs. It shares the same 3.78-inch bore and 3.62-inch stroke as other 5.3 engines but uses dished pistons for a compression ratio of roughly 9.5:1. Equipped with aluminum cylinder heads, a hydraulic roller camshaft, sequential fuel injection, and coil-near-plug ignition, the LM4 produces about 290 horsepower and 325 lb-ft of torque.

LR4

The LR4 is a 4.8-liter (293 cubic inch) iron-block Vortec V8 produced from 1999 to 2007 and commonly found in half-ton Chevrolet and GMC trucks. It features a 3.78-inch bore and shorter 3.27-inch stroke, aluminum cylinder heads, and a compression ratio of about 9.5:1 using flat-top pistons. The engine is equipped with an OHV hydraulic roller valvetrain, sequential fuel injection, and coil-near-plug ignition, producing between 270 and 285 horsepower and approximately 285 to 295 lb-ft of torque.

Frequently Asked Questions