This new iteration of the storied small-block family features a revised, larger-bore cylinder block – 4.06-inch vs. the previous 6.0L’s 4.00-inch bores – high-flow, LS7/L92-style cylinder heads; larger-diameter pistons; revised camshaft and camshaft timing; revised valvetrain with offset intake rocker arms; high-flow intake manifold, and high-flow fuel injectors from the Z06’s LS7 engine.
In addition to its larger bores, which help create a 376-cubic-inch displacement, the block
casting also features revisions and machining in the bulkheads that enhance its strength and improved bay- to- bay breathing. But while the bore of the 6.2L engine is increased when compared with the previous 6.0L engine, the engine’s stroke remains at 3.62 inches (92 mm). The pistons for the larger 6.2L engine also are new and are designed for its high-rpm performance capability.
Breathing for the 6.2L engine is accomplished via high-flow cylinder heads, based on the large port/large valve design found on the LS7 engine and L92 engines, with larger-capacity, straighter intake ports. The design optimizes intake flow to the combustion chamber. The exhaust ports are also designed for better flow.
Complementing the larger-port design of the heads are commensurately sized valves. The intake valve size increases from 2.00- inches to 2.16- inches – an increase of nearly 9 percent. The intake valves feature lightweight hollow stems, which enable the engine’s 6,600-rpm capability. The exhaust valves also are large, measuring 1.60-inches in diameter.
To accommodate the engine’s larger valves and enable more direct intake port flow, the intake-side rocker arms are offset 6 mm between the valve tip and the push rod. Actuating the valves is a new camshaft, with intake lobes providing more than a 5-percent percent in increase in lift, from 0.521-inch to 0.551-inch. Exhaust-valve lift remains unchanged from the LS2.
Ensuring the cylinder heads receive all the air they can handle falls to a new, acoustically tuned intake manifold. The composite design is manufactured with a “lost core” process that improves runner- to- runner variation and reduces airflow losses. An acoustic foam material is used to reduce radiated engine noise; it is sandwiched between the outer top of the manifold and an additional “skull cap” acoustic shell. Also new beauty covers atop the engine feature a noise-reducing, acoustically tuned insert to provide a sexier engine sound.
Exhaust system
Optional on ’08 Coupe and Convertibles is a new, two-mode performance exhaust system. Similar in design and function to the system used on the Z06, the dual-mode exhaust uses vacuum-actuated outlet valves, which control engine noise during low-load operation, but open for maximum performance during high-load operation. The Coupe/Convertible incorporates a 2.5-inch-diameter exhaust, while the Z06 uses a three-inch system. With the dual-mode exhaust, power output for Coupe/Convertible rises from 430 horsepower and 424 lb-ft of torque to 436 hp and 428 lb-ft.
