551 cams are bolt-in cams for 1999-'06 engines. Cams that exceed the limits of the stock valve springs require the use of special high lift springs. Most S&S cams have higher lift than stock and are designed to take advantage of the extra flow of ported stock heads or S&S Super Stock® heads. Due to the high lift of these cams, S&S adjustable pushrods are recommended. Not all grinds are available in the chain drive version. To get the best performance from a performance cam installation, a high flow intake and exhaust system is also recommended.
