THESE ARE OLDSMOBILE PRO MAGNUM STREET/STRIP 1.6 OLDSMOBILE STAINLESS STEEL ROLLER ROCKERS .THEY FIT ALL 3/8 ALUMINIUM HEADS OR CAST IRON HEADS WITH 3/8 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 . THESE ARE PROBABLY ONE OF THE STRONGEST EASIEST ROCKERS TO INSTALL