One of the first requirements when installing a Steel Roller cam is the addition of a bronze distributor Gear. A stock cast iron Gear is not compatible with a Steel Camshaft. COMP Cams Gears are machined from AMPCO-45 extruded aluminum bronze with 5% Nickel added. These Gears feature a high-strength tooth design that resists wear even when used with high pressure oil pumps. These extra tough Gears are the answer when higher Mechanical properties are demanded.Pontiac-4Cylinder 151 1977-78, 4Cylinder 151 1979-89 oil pump Gear, Fits Shaft Diameter 0.491".