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It is for good reason that virtually every top professional engine builder relies on ARP Pro Series head studs for their all-out competition powerplants. Simply stated, there's not a better stud setup on the market today. ARP hardware is constructed of a 8740 alloy that is rated far superior to aircraft grade hardware.
Each stud is placed vertically in special racks and precisely heat-treated to 200,000 psi. This procedure ensures complete heat penetration. Following heat-treat, each stud is centerless ground to make it as close to perfectly concentric as possible. This procedure involves about ten very slight cuts and results in an exceptionally straight part. It's important to note that lesser quality studs are not even centerless ground - the material is thread rolled in bar stock form (mostly before heat-treat, when the material is easier to machine).
Because ARP studs are manufactured to such exacting tolerances, you will note that gaskets and cylinder heads literally glide into position and are perfectly aligned - something that won't happen with inferior quality head studs. ARP studs are thread rolled after heat-treat, which gives them about 1000 times better fatigue strength than those studs that are threaded prior to heat-treat. It costs a lot more to do it this way, because it's tough on tooling, but the results are well worth the extra effort. You won't find a better quality stud on the market.
Look for ARP stamped on each stud as your assurance of quality. Clearly, ARP Head Stud/Bolt Kits are the best on the market today, and the favorite of leading professional engine builders in all forms of racing.
Note: K20A/Z head studs are compatible with K24A series engine applications. Not compatible with K24Z engines!