Dress Up Your Small Block Engine with These Stainless-steel Header bolts. These will not fit Factory cast iron exhaust manifolds. These Use a 5/16” Allen Wrench/Socket. Compatible with all 1955-1998/99 Chevy Small Block Exhaust Headers with up to ½” Thick Flanges 265 283 305 307 327 350 383 400 (These do not fit oem manifolds).
