Cyl Head Specifications: Combustion chamber vol: 64cc; Intake runner vol: 170cc; Exhaust runner vol: 70cc; Intake valve dia: 1.94"; Exhaust valve dia: 1.55"; Valve stem dia: 11/32"; Valve guides: Maganese bronze; Deck thickness: 5/8"; Valve spring diameter: 1.46"; Valve spring maximum lift: .575"; Rocker stud: 3/8"; Pushrod diameter: 5/16"; Valve angle: 23°; Exhaust port location: Stock; Spark plug fitment: 14mm x .750 reach, gasket seat. * Edelbrock E-Tec Cylinder Heads are replacements for 302, 327, 350 & 400 c.i.d. S/B Chevy engines with "Vortec-style" manifolds. They feature an LT1-style raised runner intake port design for increased air-flow and ultimate performance. A unique combustion chamber design positions the spark plug closer to the center of the cylinder, promoting a more efficient combustion resulting in more power. These cylinder heads include an adjustable rocker stud and guide plate set-up for use with adjustable rockers or washers to properly position the stud height to accommodate factory style self-aligning rocker arms. They have 20% more exhaust flow than cast iron Vortec heads, great performance up to 6000 rpm and can produce 9.5:1 compression with stock pistons in 350 cubic-inch engines. RPM E-Tec heads are dual-drilled and will accept 1987-95 centerbolt and/or 1986 & prior perimeter flange mount valve covers and most stock exhaust manifolds. ** 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 3/4" reach with flat gasket seat. To use stock rockers on S/B Chevy heads, .100" longer than stock pushrods are required. Edelbrock pushrods #9629 are recommended. Use Head Bolt Kits for easy installation. 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.