This S&S 514 cam is for 1978-1984 Harley-Davidson big twin models with 84 to 93 inch strokers and no greater than 9:1 compression ratio. The best gains occur in the mid range from 2,500 to 5,000 rpm where most riding is done. This cam is relatively quiet and easier on the valve train than most other cams with lifts as high. Valve spring spacing and other normal clearancing checks required. For solid tappet or may be used with modern high performance hydraulic tappets for shovelhead engines. Stock hydraulic tappets are not recommended. 1980-1981 engines require conversion to late style valve guides S&S Part #: 33-5052