The S&S KN420 cam is a high-lift cam for modified knuckle engines. Features .420 inch valve lift and increased duration for larger engines up to 93 inch and compression ratio of up to 8.5:1. Special high-lift valve springs are required. Designed to be used with solid lifters. Fits 1936-1947 OHV big twin engines in Harley-Davidson motorcycles and Flathead Power KN-Series engines. S&S Part #: 106-2409