Cylinder Head Specifications: Combustion chamber volume: 62cc; Intake runner volume: 195cc / 200cc; Exhaust runner volume: 68cc; Intake valve diameter: 2.02; Exhaust valve diameter: 1.60; Valve stem diameter: 5/16; Valve guides: Manganese bronze; Deck thickness: 11/16 (extra thick); Valve spring diameter: 1.45 / 1.30; Valve spring maximum lift: .690 / .650; Rocker stud: 7/16; Guideplate: Hardended steel; Pushrod diameter: 3/8; Valve angle: 5°; Exhaust port location: Stock; Spark plug fitment: 14mm x 3/4 reach, gasket seat. INSTALLATION NOTE: 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 are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat. Deck thickness: 11/16", rocker stud diameter: 7/16", pushrod diameter: 3/8" (width of slot in guide plate).