Hydraulic Flat Tappet; For '58-'98 262-400 cid Small Block Engines (Except LT1)• 50-State Legal Performance Upgrade For 1987 & Earlier Carbureted V8 Small Block Chevy*• Good Street Performance w/ Stock Converter Choppy IdleIn order to use these camshafts in 1955-57 265ci blocks it is necessary to machine a small groove in the rear main journal of the cam to allow oil flow to the top of the engine.