( C/C-12-601-20 ) - - NITRIDED THUMPER CAMSHAFT - - Hydraulic Flat Tappet, Advertised Duration 287/305, Lift .489/.476, Chevy, Small Block.---------------------------------------------------------------------------------- Nitriding is basically a surface hardening treatment. Leading valvetrain engineers and the in-house expert on the nitriding process, explains the process as, “all about getting nitrogen into iron or steel.”