Cylinder Head Specifications: Combustion chamber volume:-?64cc /68cc, Intake runner volume:-?185cc / 225cc / 260cc, Exhaust runner volume:-?75cc / 88cc, Intake valve diameter:-?2.02in (185cc) / 2.10in (225cc), Exhaust valve diameter:-?1.60in, Deck thickness:-?9/16in, Valve spring diameter:-?1.46in, Valve spring diameter:-?1.46in, Valve spring maximum lift:-?.575in, Rocker stud:-?3/8in (185cc) / 7/16in (225cc), Guideplate:-?Hardened steel, Pushrod diameter:-?5/16in, Valve angle:-?23, Spark plug fitment:-?14mm x .750 reach, gasket seat. INSTALLATION NOTE: 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. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4in reach with flat gasket seat. IMPORTANT NOTES, To use stock rockers on small-block Chevy heads, .100in longer than stock pushrods are required. Edelbrock pushrods No.9629 are recommended for use with flat tappet cams only. S/B Chevy heads may not be used on engines with less than 4in bore (262, 265, 267, 283, 305, 307 c.i.d.) except with cams having less than .450in valve lift. Replacement valve part numbers are for sets of 8.