Originally designed for S&S 4 1/8 bore V-Series engines with piston oiler jets, these high volume high pressure oil pumps also work well in stock HD Evolution engines and S&S V-Series engines. Fits 1984-'91 HD Big Twins. No thicker than a stock pump. Gears with fewer, but larger teeth provide increased oil volume for both supply and return sides of the pump. Supply gears are 9% wider than stock and standard S&S oil pumps. 28% wider than stock return gears ensure proper crankcase scavenging, reduce drag on the flywheels, and eliminate oil carryover. Polished Billet Finish. Increased scavenging capacity results in Less oil in the crankcase, Less oil carryover, Excess oil from pressure control valve is filtered & longer pump life. Equipped with a stock length oil pump drive shaft. We do not recommend the HVHP for shovel engines, as it may over oil the top end unless the oiling system is modified with the S&S valve train update kit.