ARP® uses a premium grade 8740 alloy that is rated far
superior to "aircraft" quality. Each stud is precisely heat-treated to
200,000 psi. Following heattreat, each stud is centerless ground to make
close to perfectly concentric as possible. This procedure involves about
very slight cuts and results in an exceptionally straight part. It's
to note that lesser quality studs are not even centerless ground—the
thread rolled in bar stock form (mostly before heat-treat, when the
easier to machine). Because ARP® studs are manufactured to such exacting
tolerances, you will note that gaskets and cylinder heads literally
position and are perfectly aligned—something that won't happen with
quality head studs.
ARP® studs are thread rolled after heat-treat, which gives them about
(that's ten times) better fatigue strength than those studs that are
prior to heat-treat.
ARP® aslo offers specially undercut studs for several
engines. This procedure (done only to the shorter studs) more equalizes
"stretch" of both studs, which makes for a more consistent clamping
that compensates for head gasket compression when the head is installed.