ARP Subaru WRX STI EJ20 & EJ25 DOHC Head Stud Kit ARP2001 ARP Bolts

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 is not a better stud set upon the market today.

For openers, ARP only uses premium grade 8740 alloy and a proprietary ARP2000 alloy that are rated far superior to aircraft quality alloy steels. Secondly, each stud is placed verticallyinto special racks and precisely heat-treated to 190,000 psi forthe 8740 material and 220,000 psi for the ARP2000 material. This procedure ensures complete heat penetration and the resultsare 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 exceptionallystraight part. It is important to note that lesser quality studs are not even centerless ground the material is thread rolled inbar 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 headsliterally 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 2000% (that is twenty times) better fatigue strength than those studs that are threaded prior to heat-treat (a very commonindustry practice). It costs a lot more to do it this way, because it is tough on tooling, but the results are well worth the extra effort.You will also note that ARP offers specially undercut studs for several engines. This procedure (done only to the shorter studs) more equalizes the stretch of both studs, which makes for a more consistent clamping force and one that compensates for head gasket compression when the cylinder heads are installed. This helps prevent blown head gaskets, and assures optimum engine sealing! Premium quality 8740 and ARP2000 head stud kits are availablefor most domestic and import applications. You won’t find abetter quality stud on the market from any other source. Look for ARP stamped on each stud as your assurance of quality. Clearly, they are the best on the market today, and the favorite of leading professional engine builders in all forms of racing.