Abstract: The present invention is an oil pump used in combination with a twin cam type engine, such as a HARLEY DAVIDSON® type A or type B engine, that includes a first high pressure gerotor and cam chest scavenger gerotor housing, a separator plate that establishes an independent dual scavenging capability and a second crankcase sump scavenger gerotor housing that pulls oil from the crankcase sump. The oil pump also includes a high pressure gerotor that pulls oil from an oil reservoir and supplies oil under pressure through a stock or aftermarket cam plate to the engine, a cam chest scavenger gerotor to scavenge oil in a cam chest of the engine and return the oil to the oil reservoir, a crankcase sump scavenger gerotor to scavenge the oil in a crankcase sump of the engine and return the oil to the oil reservoir and an o-ring to prevent the oil from leaking into the cam chest of the engine.