Feuling Race Lifters for Twin Cam and Sportster engines are designed to work in conjunction with the Feuling Race Pump 433-804 , 741-279 and to operate with large lift camshafts and higher spring pressures, while maintaining proper and critical oil flow to valves, springs, rockers, shafts, and valve guides Designed for engines with radical valve spring pressures and large lift camshafts Optimize valve - train stability at high RPM, decrease valve float Maintain maximum valve lift , Increase horsepower & torque output CNC-machined and precision ground Recommended for both strip and high performance street engines