5.3 L LS4 V8

The LS4 is a 5,327 cc (5.3 L; 325.1 cu in) version of the Generation IV block. Though it has the same displacement as the Vortec 5300 LY5, it features an aluminum block instead of iron, and uses the same cylinder head casting as the Generation III LS6 engine. The LS4 is adapted for transverse front-wheel drive applications, with a bell-housing bolt pattern that differs from the rear-wheel-drive blocks (so as to mate with the 4T65E). According to GM, "The crankshaft is shortened 13–3 mm (0.51–0.12 in) at the flywheel end and 10 mm (0.39 in) at the accessory drive end – to reduce the length of the engine compared to the 6.0 L. All accessories are driven by a single serpentine belt to save space. The water pump is mounted remotely with an elongated pump manifold that connects it to the coolant passages. Revised oil pan baffles, or windage trays, are incorporated into the LS4 to ensure that the oil sump stays loaded during high-g cornering."[55] Active Fuel Management is also used. Output of this version is 303 hp (226 kW)/300 hp on LaCrosse Super and 323 lb⋅ft (438 N⋅m).