ARP 1355201 High Performance Series Main 4-Bolt Kit High Performance Series main bolts are a premium replacement for OEM fasteners Designed to meet the exacting standards and demands of professional engine builders Forged from 8740 chrome moly steel, with generous under-head radius and rolled threads Rated at 180,000 PSI, which is considerably stronger than Grade 8 hardware 1000% longer fatigue life than most other main bolts