Cylinder Head Specifications: Combustion chamber volume: 110cc / 118cc; Intake runner volume: 290cc; Exhaust runner volume: 110cc; Intake valve diameter: 2.25"; Exhaust valve diameter: 1.89"; Valve stem; diameter: 11/32"; Valve guides: Manganese bronze; Deck thickness: 9/16"; Valve spring diameter: Hydraulic Roller (#61555); Valve spring maximum lift: N/A; 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. * Match with Edelbrock head gasket sets. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat. Deck thickness: 9/16", rocker stud diameter: 7/16", pushrod diameter: 3/8" (width of slot in guide plate). 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. Deck thickness: 9/16", rocker stud diameter: 7/16", pushrod diameter: 3/8" (width of slot in guide plate). All Performer and Performer RPM B/B Chevy heads have spark plugs relocated closer to center of bore which will interfere with high-dome pistons for open chamber heads. Use pistons designed for our heads. Deck thickness: 3/4", pushrod diameter: 7/16". Replacement valve part numbers are for sets of 8.