Chevy Small Block Cast Iron Vortec Complete Assembly

America's favorite high performance cast iron small-block cylinder heads offer big power and bigger value. The GM (Chevy) Vortec cylinder heads fast burn combustion chamber and high velocity ports combine to produce big horsepower out of the box. Vortec heads can be mildly ported for additional performance and can be milled up to .040'' for increased compression ratio. The Vortec head uses 1.94'' intake valves and 1.50'' exhaust valves to compliment the high velocity port design. The Vortec head out-flows the bow-tie head out of the box and is a 20 to 40 horsepower bolt-on increase over earlier cast iron small-block heads. Vortec Heads require a Vortec style intake manifold due to its improved manifold mounting flange and gasket design and raised intake ports. It is not recommended that the heads be modified to accept early design intake manifolds. Vortec heads fit all small-block engines produced 1955 to present, excluding LT1/LT4 reverse coolant flow engines and current LS1 style engines. Vortec heads come completely assembled with valves, springs, retainers, and 3/8'' rocker studs. Requires the use of self-aligning rocker arms.