This S&S 561 cam is for 1984-1999 Harley-Davidson big twin models. This cam is recommended for 88 to 96 inch engines with 9.5:1 to 10.5:1 compression ratio. Provides strong midrange power. 3000-5500 rpm. Requires hydraulic tappets and spring spacing. View Cam Specs S&S Cam Specifications for 1984-'99 Big Twin Engines Cam Name Valve Timing Open/Close Valve Duration Valve Lift Lift @ TDC Spring Spacing RequiredTappet Type Required Part # Intake Exhaust Intake Exhaust Intake Exhaust 561 32*/40* 50*/26* 252* 256* .560" .252" .210" Yes Hydraulic 33-5076 Timing designation is function of zero lash @ .053" off base circle. Lifts @ TDC are measured at the valve and are for reference only. Overlap valve lifts must be checked on assembled motors. S&S Part #: 33-5076