12556463 - GM Performance Parts SB-Chevy ZZ4 Aluminum Heads Details
No heat riserAngled spark plugs (5/8 hex, 3/4" reach, tapered plugs)1.48" Valve spring seat diameterScrew-in studs (3/8" top, 7/16" bottom)Use head gaskets with stainless steel fire ringsRaised, machined rocker railsExhaust ports are raised .100", requires Fel-Pro gasket #375-1470Use rail type Rocker P/N 10089648, or kit P/N 12370838