COMP Cams CL11-600-4 Thumpr 227/241 Hydraulic Flat Cam and Lifter Kit for Chevrolet Big Block 396-454 High performance street, stock converter ok, best with 2000+ converter and gears. Choppy/thumping idle. 1,800-5,600 RPM Operating Range 227/241 Duration at .050". 107 Degree Lobe Separation Angle. 0.498"/0.483" Valve Lift CL Kits include a camshaft, a set of lifters, instructions and assembly lubricant. Early intake valve opening and long exhaust duration create optimum overlap for powerful, hard-hitting exhaust note. Best with aftermarket converters and more rear gear. Perfect choice for muscle cars and street rods - Three unique cam designs: Thumpr, Mutha' Thumpr and Big Mutha' Thumpr deliver excellent horsepower gains and broad torque curve. Fits Chevrolet 396-454 Mark IV Big Block Made in USA