Competition Cams 12-601-4 Mutha' Thumpr 287TH7 Camshaft for Small Block Chevy HYDRAULIC - Mutha' Thumpr: High performance street/strip, needs 9:1 compression, 2500+ stall, intake, gears and headers, rough idle. 287/305 Advertised Duration, 235/249 Duration @ .050 inch, .489 inch/.476 inch Lift, 107 Lobe Separation Valve spring upgrade required