Designed for big-block Chevy 396-502 c.i.d. engines, these oval port heads feature 100cc semi-open combustion chambers created by angle milling at a 1.5 degree angle to improve intake port alignment and create a smaller chamber without valve shrouding. Using stock flat top style pistons they create an ideal street compression ratio of 9.2:1 without the need to purchase aftermarket domed pistons. A totally unique intake port design yields flow numbers traditionally associated with high performance rectangular port heads, but with the smaller runner size and velocity of an oval port for excellent seat-of-the-pants performance and crisp throttle response. The stainless steel 2.19' intake and 1.88' exhaust valves have smaller-than-stock 11/32' valve stems to promote excellent flow and lighter valve weight. The deck surface and water jackets were specially designed to work with all big-block Chevrolet engine blocks. The heat crossover passage is present, but has been blocked, making these heads not legal for use on emissions controlled engines. Heads include top-quality ARP rocker studs, bronze guides and hardened, ductile iron valve seats.