Designed and developed for Zippers by the Axtell Mountain Motor team. This is a precision-machined "needle and seat" that inserts in place of the factory oil pressure relief valve in the cam plate. With the factory OEM oiling system configuration, when oil pressure becomes excessive, it is bypassed from the high pressure side of the feed gerotor back to the low pressure side, "looping" the oil in the feed gerotor gears. This causes the introduction of air into the pressurized oil, making the oil foamy and spongy, resulting in lower oil pressure and volume. When this occurs, the entire oiling system is affected - engine heat and noise builds, piston oilers shut down sooner than designed, valve train and top end life is shortened. The Zippers bypass valve blocks the factory port back to the feed side of the pump and directs the bypassed oil into the cam chest. The scavenge side of the oil pump returns the excess oil to the oil tank and eliminates the oil "looping" and its negative effects as described above. Fits stock Twin Cam and Screamin' Eagle cam plates 1999-2017.