High Volume High Pressure Oil Pump Kit With Gears for 1984-'91 HD® Big TwinsOriginally 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