3l v6Holds the cam backFits applications1977-1980 - Buick1955-1986 - Chevrolet1977-1980 - Oldsmobile The thrust button rides between the front of the timing gear and the back of the front cover, and shimmed for proper end play in the cam. Both solid nylon button and roller thrust bearing styles..COMP Cams 202 Nylon Thrust Buttons & Wear Plate Wear plates eliminate the wear at the front of the block and are moly coated.