This high quality cylinder head bolt kid has enough bolts to install either iron or aluminum heads. This kit includes eight of 7/16" - 14 x 2.08" short bolts P/N 12367331, 24 of 7/16" - 14 x 4.06" long bolts P/N 12367330, eight of 7/16 - 14 x 5.06" extra long bolts P/N 12367329, and 40 of special hardened washers P/N 14011040. For single service replacement use part numbers above. These bolts do not have thread sealer on them because on 502 engines they have blind bolt hold. For all other big block usage, add thread sealer. Technical Notes: When you complete your engine you will have left overs because this is a universal kit for both iron and aluminum heads.