ARP Mitsubishi 4G63 M12 head stud kit
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.
For openers, ARP only uses premium grade 8740 alloy and a proprietary ARP2000 alloy that are rated for superior to "aircraft" quality alloy steels. Secondly, each stud is placed vertically into special racks and precisely heat-treated to 200,000 psi for the 8740 material and 220,000 psi for the ARP2000 material. This procedure ensures complete heat penetration and the results are far superior to those lesser quality studs from other manufacturers who just dump pieces in a basket and hope for the best.
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.