THESE ARE NOT HEAD STUDS! Our ARP Main Cap Stud Kits include the appropriate amount of studs, parallel ground washers, and 12 point nuts for 1 engine. Our ARP Main Cap Bolt Kits include the appropriate amount of 12 point main cap bolts and parallel ground washers for 1 engine.

ARP Main Cap Studs and Bolts help reinforce engines for high performance use. Crankshaft main caps or "mains" are what supports an engines crankshaft and main bearings. The hardware used to fasten main caps to the engine block must deal with high levels of stress during operation (especially when using turbo, superchargers, nitrous or high compression). Often OEM hardware is not up to the task of supporting engines with high power levels, which can lead to failures including crankshaft instability, damage, main cap "fretting" and possibly other issues.

The best way to prevent fastener failure is to upgrade the strength of your bolts and studs. ARP has been providing high strength fasteners for over 40 years and they have been the main choice in automotive performance hardware for almost all forms of professional motorsports. These main cap studs and bolts are manufactured using the highest quality 8740 chrome moly steel, heat treated to 200,000 PSI tensile strength and thread rolled after heat treating. This creates a fastener with threads that are thousands of times stronger than others and able to withstand large amounts of strain from high performance engines. If you need to replace compromised OEM hardware or are simply re-building an engine for high performance use, don't settle for anything lest than the best!

Installation Notes: Although these can be installed easily, we recommend having engine main journals professionally measured after install and line honed if need be. Since the ARP hardware can provide greater clamping power than stock bolts, journal bores can distort if torqued higher than original values. Always follow the included ARP instructions during your install for best results.