ARP 207-4702 undercut (U/C) head stud kit Mitsubishi Lancer Evo IV, V, VI, VII, VIII, IX, Eclipse 4G63T M11 (8740 Cro-Mo)
For: Mitsubishi Lancer Evo IV, V, VI, VII, VIII, IX, Eclipse with 4G63T engines
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 far superior to “aircraft” quality alloy steels. Secondly, each stud is placed vertically into special racks and precisely heat-treated to 190,000 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. 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 2000% (that’s twenty times) better fatigue strength than those studs that are threaded prior to heat-treat. It costs a lot more to do it this way, because it’s 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 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!
