ARP Main Bolt Kits | Multiple Chevrolet Fitments (135-5201)Main Bolt Kit by ARP ARP Pro Series main bolts are application specific and rated at 190,000 psi. Designed for use in competition engines, as well as to meet the exacting standards and demands of professional engine builders, ARP bolts are forged from 8740 chromoly steel and feature a reduced wrenching head, large underhead radius, and rolled threads for the utmost in reliability. The threads are rolled after heat treating which gives them about 2,000