(11mm) Built for the Mitsubishi EVO (03-07)...
Obtaining the optimum cylinder head-to-block sealing is especially critical in small displacement engines employing high compression pistons or power adders like turbochargers, nitrous oxide, and superchargers.
That's why head studs from ARP are popular among leading Sport Compact/Import racers.
You should know that a premium grade 8740 alloy is used by ARP that is rated far superior to 'aircraft' quality.
Then, each stud is precisely heat-treated to 200,000 psi.
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% (that's ten times) better fatigue strength than those studs that are threaded prior to heat-treat.
You will also note that specially undercut studs for several engines are offered by ARP.
This procedure (done only to the shorter studs) more equalizes the 'stretch' of both studs, which makes for a more consistent clamping force—one that compensates for head gasket compression when the head is installed.
This helps prevent blown head gaskets and assures optimum sealing!
