COMP Cams CL11-602-4 Thumpr 243/257 Hydraulic Flat Cam and Lifter Kit for Chevrolet Big Block 396-454 Street/strip, needs 9.5:1 compression, 2800+ stall, intake, gears and headers, very rough idle. 2,300-6,200 RPM Operating Range 243/257 Duration at .050". 107 Degree Lobe Separation Angle. 0.522"/0.507" 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