ARP 1355601 4-Bolt Main Stud Kit Main studs are designed to meet the exacting standards and demands of professional engine builders Manufactured from 8740 chrome moly steel Rated at 200,000 PSI, which is considerably stronger than Grade 8 hardware Rolled J-form threads are 1000% stronger than other threads Main studs are recommended over main bolts for a number of reasons, including more accurate torque readings and easier engine assembly