The Gen-V small-block’s all-new cylinder head design builds on the excellent, racing-proven airflow attributes of previous small-block heads and matches it with an all-new direct-injection combustion system. It supports tremendous airflow at higher rpm for a broad horsepower band, along with strong, low-rpm torque.
Compared to the Gen-IV cylinder head design, the LT1 head features a smaller, 59.02cc combustion chamber. It is designed to complement the volume of the piston’s dish. The smaller chamber size and dished pistons work together to produce an 11.5:1 compression ratio. The spark plug angle and depth have been modified to protrude farther into the chamber, placing the electrode closer to the center of the combustion to support the direct injection system.
In addition to the new combustion chamber design, the Gen-V head features large, straight and rectangular intake ports that feature a slight twist to enhance mixture motion. This is complemented by a reversal of the intake and exhaust valve positions as compared to the Gen-IV design. The exhaust port shapes are optimized for the new valve locations, with new port opening locations at the manifold face.
Large, lightweight intake and exhaust valves are used in the aluminum alloy heads, with 2.13-inch (54mm) hollow intake and 1.59-inch (40.4mm) hollow sodium exhaust valves. The lightweight valves enable the engine to rev quickly and capably to greater than 6,000 rpm.
The valves are held at new 12.5 degrees intake/12 degrees exhaust angles vs. the Gen-IV’s 15-degree angle. Additionally, the valves are splayed at 2.61 degrees intake/2.38 degrees exhaust to reduce shrouding and enable greater airflow.
Valvetrain components include durable valve springs and roller-pivot rocker arms with a 1.8 ratio – the amount of movement on the valve side of the rocker arm in comparison with the pushrod side. And speaking of pushrods, the Gen-V small-block features stiffer, larger-diameter 8.7mm (outside diameter) that provide greater stiffness than the previous 7.9mm design. This enables improved high-speed valvetrain dynamic performance.
The heads are made with 319-T7 aluminum alloy, using a semi-permanent mold process that produces a more accurate casting for optimal mass reduction and minimal machining.