Cylinder Head Specifications; Combustion chamber volume: 16cc; Intake runner volume: 215cc; Exhaust runner volume: 115cc; Intake valve diameter: 2.19; Exhaust valve diameter: 1.72; Valve stem diameter: 11/32; Valve guides: Manganese bronze; Deck thickness: 9/16; Valve spring diameter: 1.55; Valve spring maximum lift: .600; Rocker stud: 7/16; Guideplate: Hardended steel; Pushrod diameter: 3/8; Valve angle: 0°; Exhaust port location: Stock; Spark plug fitment: 14mm x 3/4 reach, gasket seat ** Use Edelbrock head gasket sets. May be used on 348 engines with valve lifts up to .550 only. 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. These heads will only fit 1958-65 348 c.i.d. W engines if an Edelbrock #5409, #7159 or stock large port 409 c.i.d. manifold is used. Proper cylinder wall notching must be checked to ensure exhaust valve to cylinder clearance. Deck thickness: 9/16, rocker stud diameter: 7/16, pushrod diameter: 3/8 (width of slot in guide plate).