The Edelbrock part # 77119 LT1 (Gen V) Performance RPM cylinder heads are ideal for street engines and are engineered to be a great high-performance upgrade for stock GM Gen V LT1 engines. It has been designed with a thicker deck and more material in the intake, exhaust and port walls for improved strength and durability. This cylinder head features CNC machined chambers as well as CNC blended valve seats, intake and exhaust ports for consistency. They have been designed with high flow intake, exhaust ports and back cut intake valves for improved air flow. The valve position has also been revised to accommodate interlocking valve seat rings and larger valves. The Performer RPM retains the stock rocker arm, intake/exhaust ports and spark plug location for use with factory components. Like all of our other cylinder heads, these have been designed, tested and cast from 356 aluminum and heat treated to T-6 specs in our facilities in Southern California to guarantee you get the best from a name you can trust. - Combustion chamber volume: 58cc - Intake runner volume: 305cc - Exhaust runner volume: 115cc - Intake valve diameter: 2.165" - Exhaust valve diameter: 1.600" INSTALLATION NOTE: Match with Edelbrock head gasket sets. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat.