THESE ARE OLDSMOBILE PRO STREET 1.6 OLDSMOBILE ALUMINUM ROLLER ROCKERS .THEY FIT ALL 7/16 ALUMINIUM HEADS OR CAST IRON HEADS WITH 7/16 STUDS . THESE ROCKERS FIT ALL 1964 TO 1987 OLDSMOBILE 307,330,350,403 SMALL BLOCK , AND 400,425,455 BIG BLOCK ENGINES . THEY ARE DESIGNED TO TAKE UP TO 650 LIFT .