Edelbrock part #75621 RPM Air-Gap 2-R intake manifold is designed for street 396-502 c.i.d. Chevrolet V8's with high-performance rectangular-port heads. The open air space separates the runners from the hot engine oil, and as a result, the air/fuel mixture stays cooler for a denser charge and more power. This intake manifold is a dual-plane, high-rise design with a 180 degree firing order to produce incredible top-end horsepower while retaining good throttle response. The larger plenum and runners match the free-flowing exhaust, high-lift cams and other modifications of a high output engine. They are intended for high-performance's street or competition engines that run up to 6500 rpm. Includes rear water outlets, two distributor clamp locations and nitrous bosses. Accepts all late model alternator and A/C brackets for the street. For square-bore carbs only. No provision for exhaust heated chokes and no exhaust crossover. This manifold offers a polished finish for a brilliant shine and classic look.