Cylinder Head Specifications: Combustion chamber volume: 118cc; Intake runner volume: 315cc; Exhaust runner volume: 110cc; Intake valve diameter: 2. 19"; Exhaust valve diameter: 1. 88"; Valve stem diameter: 11/32"; Valve guides: Manganese bronze; Deck thickness: 9/16"; Valve spring diameter: 1. 55"; Valve spring maximum lift: . 700"; Rocker stud: 7/16"; Guideplate: Hardened steel; Pushrod diameter: 3/8"; Valve angle: 26°; Exhaust port location: Stock; Spark plug fitment: 14mm x 3/4 reach, gasket seat. INSTALLATION NOTE: Bare heads will have valve guides & seats installed, but will require final sizing & a valve job to match the valves you will be using. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat. All Performer and Performer RPM Big-Block Chevy heads: Spark plug is closer to center of bore, will interfere with high-dome pistons for open chamber heads. Use pistons designed for our heads. Match with Edelbrock head gasket sets.