Cylinder Head Specifications: Combustion chamber volume: 60cc; Intake runner volume: 190cc; Exhaust runner volume: 90cc; Intake valve diameter: 2. 05"; Exhaust valve diameter: 1. 60"; Valve stem diameter: 11/32"; Valve guides: Manganese bronze; Deck thickness: 5/8"; Valve spring diameter: 1. 55"; Valve spring maximum lift: . 580"; Rocker stud: 7/16"; Guide plate: Hardened steel; Pushrod diameter: 5/16"; Valve angle: Same as OE 9. 5°; Exhaust port location: Stock; Spark plug fitment: 14mm x 3/4 reach, gasket seat. INSTALLATION NOTE: Match with Edelbrock head gasket sets on pages 84-85. Bare heads will have valve guides and seats installed, but will require final sizing and a valve job to match the valves you will be using. Recommended spark plugs 14mm x 3/4" reach with flat gasket seat (Champion RC12YC). Deck thickness: 5/8", rocker stud diameter: 7/16", pushrod diameter: 5/16" (width of slot in guide plate). Valve sizes are recommended, not maximum. IMPORTANT NOTE: "Compact charge" kidney shape combustion chamber design. Intake and exhaust ports based on 2V design. Optimized spark plug location provides improved header clearance. Bare heads will have valve guides and seats installed, but will require final sizing and a valve job to match the valves you will be using. Deck thickness: 5/8", rocker stud diameter: 7/16", pushrod diameter: 5/16" (width of slot in guide plate). Valve sizes are recommended, not maximum. Performer RPM Clevor cylinder heads with 7/16" bolts on 289/302 engines, use Edelbrock stepped head bolt washer kit #9680.