These S&S® CNC ported B3 cylinder heads are original equipment on S&S® T143 engines. They are set up for 4.425" bore and are machined for the S&S® 4-3/8" cylinder stud pattern. Kit includes front and rear head assemblies complete with S&S® .650" lift valve springs, and 2.200" intake and 1.800" exhaust valves, head gaskets, base gaskets, exhaust gaskets, and head bolts.