Competition Cams 12-600-4 Thumpr 279TH7 Camshaft for Small Block Chevy HYDRAULIC - Thumpr : High performance street, stock converter ok, best with 2000+ converter and gears. Choppy/thumping idle. 279/297 Advertised Duration, 227/241 Duration @ .050 inch, .479 inch/.465 inch Lift, 107 Lobe Separation Valve spring upgrade required