Product Overview:- Far Superior To Any Other Main Bolt Kit Offered For Use In Competition Engines, Arp Main Bolts Are Designed To Meet The Exacting Standards And Demands Of Professional Engine Builders. Forged From 8740 Chrome Moly, All Bolts Feature Generous Under-Head Radius And Rolled Threads For The Utmost Reliability. The Threads Are Rolled After Heat-Treating, Which Makes Them About 1000Percent Longer Fatigue Life Than Most Main Bolts, Which Are Threaded Prior To Heat-Treating. Available In The Popular High Performance Series, Which, At A Nominal Rating Of 180,000 Psi, Is A Premium Replacement For Oem Fasteners, Or The 200,000 Psi Nominal Rated Pro Series, Application-Specific Main Bolts With Reduced Wrenching Head And Are Designed For Use In Competition Applications. Parallel-Ground, Hardened Washers Are Included With Each Kit. Product Info:- Arp Compatible With Fo-Rd Modular V8 Main Cap-Side Bolt (Early Cast Iron Block) M8 Main Bolt KitManufacturer Part Number:- Part Number: 156-5201Item Description:- Compatible With Fo-Rd Modular V8 "Early Cast Iron Block" M8- Socket Size(S): 7/16 12Pt