Nestled inside the cylinder block is a forged steel crankshaft that delivers the LS9's 3.62-inch (92 mm) stroke. It features a smaller-diameter, ignition-triggering reluctor wheel and a nine-bolt flange-the outer face of the crankshaft on which the flywheel is mounted-that provides more clamping strength. Other non-supercharged 6.2L engines, such as the base Corvette's LS3, have a six-bolt flange. A torsional damper mounted to the front of the crankshaft features a keyway and friction washer, which also is designed to support the engine's high loads.
Attached to the crankshaft is a set of titanium connecting rods and forged aluminum pistons, which, when combined with the cylinder heads, delivers a 9.1:1 compression ratio. This combination is extremely durable and lightweight, enabling the LS9's high-rpm capability.
Cylinder Head Details
The basic cylinder head design of the LS9 is similar to the L92-type head found on the LS3 V-8, but it is cast with a premium A356T6 alloy that is better at handling the heat generated by the supercharged engine, particularly in the bridge area of the cylinder head, between the intake and exhaust valves.
In addition to the special aluminum alloy, each head is created with a rotocast method. Also known as spin casting, the process involves pouring the molten alloy into a rotating mold. This makes for more even distribution of the material and virtually eliminates porosity-air bubbles or pockets trapped in the casting-for a stronger finished product.
Although the heads are based on the L92 design, they feature swirl-inducing wings that are cast into the intake ports. This improves the mixture motion of the pressurized air/fuel charge. The charge enters the combustion chambers via titanium intake valves that measure 2.16 inches (55 mm) in diameter. Spent gases exit the chambers through 1.59-inch (40.4 mm) hollow-stem, sodium-filled exhaust valves. The titanium intake and sodium-filled exhaust valves are used for their lightweight and high-rpm capability. To ensure sealing of the pressurized engine, unique, four-layer steel head gaskets are used with the LS9's heads.
Camshaft and Valvetrain Details
The broad power band enabled by the LS9's large-displacement supercharger allows it to make strong low-end torque and great high-rpm horsepower, which allowed engineers to specify a camshaft with a relatively low lift of 0.555-inch (14.1 mm) for both the intake and exhaust valves. This low-overlap cam has lower lift and slower valve-closing speeds than the Z06's 505 hp (377 kW) LS7, helping the LS9-with its approximately 620 hp-deliver exemplary idle and low-speed driving qualities.
The camshaft actuates a valvetrain that includes many components, such as the lifters, rocker arms, and valvesprings, of the LS3 engine. However, LS7 retainers are used to support the engine's high-rpm performance.
Supercharger and Charge Cooler Details
The LS9's R2300 supercharger is a sixth-generation design from Eaton, with a case that is specific to the Corvette application. The supercharger features a new four-lobe rotor design that promotes quieter and more efficient performance, while its large, 2.3-liter displacement ensures adequate air volume at high rpm to support the engine's high-horsepower aspiration. Maximum boost pressure is 10.5 psi (0.72 bar).
The supercharger is an engine-driven air pump that contains a pair of long rotors that are twisted somewhat like pretzel sticks. As they spin around each other, incoming air is squeezed between the rotors and pushed under pressure into the engine-forcing more air into the engine than it could draw under "natural" aspiration. The rotors are driven by a pulley and belt that are connected to the engine's accessory drive system.