The S&S 560S cam is for 1978-1984 Harley-Davidson big twin models with 88 to 103 inch engines between 9:1 to 10:1 CR - excellent power across the rpm range. 3,500 - 6,000 rpm. Not recommended for stock displacement or lower compression engines. High lift valve springs and normal clearance checks required. Solid lifters or aftermarket hydraulic tappets recommended. Solid lifters or aftermarket hydraulic tappets recommended. 1980-1981 engines require conversion to late style valve guides S&S Part #: 33-5061