Cylinder Head Specifications: Combustion chamber volume: 65cc / 70cc; Intake runner volume: 185cc & 195cc; Exhaust runner volume: 65cc; Intake valve diameter: 2.02"; Exhaust valve diameter: 1.60"; Valve stem diameter: 11/32"; Valve guides: Maganese Bronze; Deck thickness: 9/16"; Valve spring diameter: 1.46"; Valve spring maximum lift: .575"; Rocker stud: 3/8"; Guideplate: Hardened steel; Pushrod diameter: 5/16"; Valve angle: 23°; Exhaust port location: Stock; Spark plug fitment: 14mm x .750 reach, gasket seat. * Performer RPM Cylinder Heads have all of the same great features as our Performer series heads, but are available with straight or angled spark plug configuration to fit a variety of exhaust applications. Available with a polished finish for a show quality look! ** Match with Edelbrock head gasket sets. 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. To use stock rockers on small-block Chevy heads, .100" longer than stock pushrods are required. Edelbrock pushrods #9629 are recommended. Use Head Bolt Kits for easy installation. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat. S/B Chevy heads may not be used on engines with less than 4" bore (262, 265, 283, 305, 307 c.i.d.) except with cams having less than .450" valve lift.