GM Performance 12497186 - GM Performance Parts Aluminum Vortec SBC Heads

This all new 23° fast burn Vortec cylinder head has the highest performance potential of any 23° SB head developed by GM using flat top pistons. This head is a bolt-on 30 hp increase when used on GM's ZZ4 crate engine. 62cc fast burn combustion chambers produce higher cylinder pressures by burning more of the available fuel before the piston starts its power stroke downward. Heads and rocker rails are CNC machined to exacting tolerances, thus eliminating the need for ''blue-printing'' of machined tolerances. ''D'' shaped 78cc exhaust, and 210cc intake port and runners require no additional porting, but is recommended for all out racing. Fits all, 1958 to present, 283-400ci SB V-8 engines with conventional water flow design; but cannot be used on any LT1, LT4 or LS1 engine with reverse water flow. Comes completely assembled with valves, springs, retainers, and 3/8'' rocker studs. Requires the use of self-aligning rocker arms.