Bare; Unported; These Cylinder Heads Can Not Be Used Without Professional Head Preparation; For Use With GM LS Series Engines; 5.6 Degree X 2 Degree Valve Angle; 25CC Combustion Chamber; 1.32 Inch X 1.97 Inch Intake Port Entry; 1.55 Inch X 1.30 Inch Exhaust Port Exit; Use With 2.25 Inch Intake Valves And 1.68 Inch Exhaust Valves; Hot Isostatic Pressing (HIP) Process; Natural; Aluminum; Single; Valve Guides Included But Not Installed