The Difference Between The LQ4 And The LQ9

LQ4 and LQ9 were code designations for the General Motors Generation III 6.0-liter, V-8 engines that were used in the company's truck applications in the mid-2000s. These engines saw duty in several GM trucks in the Chevrolet and Cadillac product lineup. The LQ9 is a high-performance version of the LQ4.

LQ4

The LQ4 was referred to as the Vortec 6000 by General Motors. The engine had 366 cubic-inch displacement, 4.0-inch bore and 3.622-inch stroke. The engine featured 300 to 325 horsepower and 360 to 370 foot-pounds of torque, depending upon the type of engine heads -- early models were equipped with cast-iron heads. In 2005, GM began putting the LQ9 floating wrist pin rods in the LQ4 engines, but the company utilized dished pistons instead of flat-top pistons.

LQ9

Introduced in 2006, the LQ9 was referred to as the Vortec HO 6000 or VortecMAX. It was a high-output version of the LQ4. The LQ9 was equipped with flat-top pistons and floating wrist pin rods. The flat-top pistons allowed for an increase in compression, and the engine produced slightly more power than the LQ4 -- plus-10 horsepower and plus-10 foot-pounds of torque.

Visual Distinctions

Visual identification between the two engines is very difficult, since the primary difference is the pistons and wrist pin rods, which are part of the engine's rotating assembly and thus enclosed in the engine block.

Replacement

The LQ4 was replaced by the LY6, a General Motors Generation IV engine that incorporates variable valve timing. The LQ9 was replaced by the L76, which incorporates an all-aluminum block in addition to variable valve timing.