These camshafts are for 1954-'84 big twins with either the Hydraulic Conversion kit or the Cylinder Head Replacement kit for panhead engines. They are also replacement parts for P-Series and SH-Series engines. Since these kits and engines include 1984-'99 style hydraulic lifters,the larger late style roller diameter requires that cams designed for 1984-'99 models must be used to achieve correct valve timing. When choosing a late style cam for this type of engine, be aware that, due to the approximate 1.5:1 rocker ratio of most aftermarket rocker arms for shovelheads, the total valve lift will be reduced by about 9% from the specified value. The specification chart shown here shows specs as used in a pan or shovel engine.