Rocker Arm Poly Lock Nut Set Chevy sb 400 350 327 307 305 283 3/8" Stud. These can be used on small block Chevy 262, 265, 267, 283, 302, 305, 307, 327, 350 and 400 V8 engines with stamped steel style rocker arms. They can be used on small block Ford 289, 302 and 351 engines with stud mounted cast style rocker arms.