The S&S Hot Set Up® kit for Twin Cams allows a Twin Cam owner to convert a stock engine to 124" using the stock crankcases. Include S&S heads 91cc, 4.125” bore cylinders and forged 10.8:1 flattop pistons, S&S 4.625” stroke flywheel assembly, S&S .640” lift gear drive Easy Start cams, tappets, S&S adjustable pushrods, roller rocker arms, and all hardware, gaskets and instructions. Fuel system is not included. Made in the U.S.A.. This project requires crankcase modifications. It is the responsibility of the person assembling the parts to check all clearances and assembly specifications.