ARP Cylinder Head Stud Kit

The ARP 218-4701 is a Pro Series cylinder head stud kit engineered for Mazda Miata vehicles equipped with 1.6L (B6) and 1.8L (BP) DOHC engines, covering model years from 1990 to 2005. This kit replaces the factory cylinder head bolts with high-strength studs, nuts, and parallel-ground washers. This conversion is crucial for engines modified to handle higher boost levels or to extract more power than the stock configuration can safely support. The primary benefits include eliminating cylinder head lifting and protecting the integrity of the threads in the engine block. Constructed from premium grade 8740 chrome moly steel, each stud undergoes a precise heat-treatment process to achieve a tensile strength of 190,000 psi. ARP's meticulous manufacturing process includes centerless grinding for concentricity and rolling J-form threads after heat-treatment, resulting in studs with approximately 1000% greater fatigue strength compared to studs threaded prior to heat-treatment. This ensures exceptional durability and reliability under demanding conditions. ARP also utilizes specially undercut studs for some applications to equalize stud stretch, promoting consistent clamping force and compensating for head gasket compression. This design aids in preventing blown head gaskets and ensures optimal engine sealing, especially critical in high-performance or boosted applications.