Bare; Unported; These Cylinder Heads Can Not Be Used Without Professional Head Preparation; For Use With Big Block Chevy Engines; 4.84 Inch Bore Spacing; 11 Degree Valve Angle; 2.52 Inch X 2.15 Inch Intake Port Entry; 1.84 Inch X 1.50 Inch Exhaust Port Exit; Use With 2.52 Inch Intake Valves And 1.90 Inch Exhaust Valves; Hot Isostatic Pressing (HIP) Process; Natural; Aluminum; Single; Valve Guides Included But Not Installed