(RB20/25 DET head stud kit) Built for the (89-98) Nissan Skyline.
In small displacement engines employing high compression pistons or power adders like turbochargers, nitrous oxide, and superchargers, obtaining the optimum cylinder head-to-block sealing is especially critical.
ARP head studs are popular among leading Sport Compact/Import racers for this reason.
A premium grade 8740 alloy, rated far superior to 'aircraft' quality, is used by ARP.
Each stud is precisely heat-treated to 200,000 psi.
After heat-treat, each stud is centerless ground to achieve close to perfectly concentric dimensions.
This procedure involves about ten very slight cuts, resulting in an exceptionally straight part.
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.
Manufactured to such exacting tolerances, ARP studs allow gaskets and cylinder heads to glide into position and align perfectly, which does not happen with inferior quality head studs.
After heat-treat, ARP studs are thread rolled, giving them about 1000% (ten times) better fatigue strength than those threaded prior to heat-treat.
ARP also offers specially undercut studs for several engines.
This procedure, done only to the shorter studs, equalizes the 'stretch' of both studs, resulting in a more consistent clamping force that compensates for head gasket compression when the head is installed.
This helps prevent blown head gaskets and assures optimum sealing.
