The heart of the Pontiac G8 GXP is the 6.2L LS3 small-block V-8, currently rated at 402 horsepower (300 kW) and 402 lb-ft of torque (546 Nm) pending final SAE certification. This engine is the newest member of GM's small-block V-8 family. It features a revised, larger-bore cylinder block, high-flow, L92-style cylinder heads; larger-diameter pistons; unique camshaft and camshaft timing; revised valvetrain with offset intake rocker arms; high-flow intake manifold; and high-flow fuel injectors.
The LS3 engine has an aluminum cylinder block with cast-in-place iron cylinder liners. Larger bores help create a 376-cubic-inch displacement. The block casting also features revisions and machining in the bulkheads to enhance its strength and improve bay-to-bay breathing. New pistons were designed for high-rpm performance.
New, high-flow cylinder heads aid engine breathing and are based on the large port and valve design found on the LS7 engine and other GM L76 engines. The larger-capacity, straighter intake port-design optimizes intake flow to the combustion chamber, an effect augmented by large valves, measuring 2.16 inches (55.0 mm) on the intake side and 1.59 inches (40.4 mm) on the exhaust side.
Pending final testing, the Pontiac G8 GXP is expected to deliver 0-to-60 mph performance of about 4.7 seconds, and a quarter-mile time of 13.0 seconds at 108 mph.
Source: Pontiac Press Release