ARP Head Stud Kit (8740 Alloy) 2014+ Fiesta ST
Virtually every top professional engine builder relies on ARP Pro Series head studs for their all-out competition power plants. Simply stated, there?s not a better stud setup on the market today.
ARP use a premium grade 8740 alloy that is rated far superior to "aircraft? quality. Each stud is placed vertically in special racks and precisely heat-treated to 200,000 psi. 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. 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 (a very common industry practice). 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.
Premium quality heat-treated 8740 chrome moly steel head stud kits are available for most applications.
Always look for ARP stamped on each stud as your assurance of quality.
HIGH PERFORMANCE SERIES: High Performance head bolts are available with a reduced wrenching hex or 12-point and wide area flanged head that eliminates the need for valve train removal to facilitate cylinder head retorquing. All High Performance Series bolts are 180,000 psi (which is 15% stronger than Grade 8) and kits come complete with hardened parallel-ground washers.
PRO SERIES: All Pro Series bolts are cold-forged to ensure molecular integrity, heat-treated prior to thread rolling and machining, and are rated nominally at 200,000 psi. ARP Pro Series head bolt kits are application specific ? designed for use with typically competition only components. These fasteners deliver superior strength and meet the ARP "ZERO defect ? ZERO failure? quality standard. Hardened and parallel-ground washers are included with each kit to ensure even load distribution and accurate torque readings. All Pro Series head bolts have a reduced wrenching hex or 12-point head and wide area flange to eliminate the need for valve train removal for cylinder head retorquing and permits the use of larger diameter valve springs. Most applications have undercut short bolts that can help eliminate head gasket failures through providing more "stretch? to compensate for the additional compression of gaskets.
Your stud should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. Remember, an undercut shorter stud will have a rate similar to a longer, standard shank stud. This provides a more even clamping force on the head. Because the head gasket will compress upon initial torqueing, make sure studs and bolts are re-torqued after the engine has been run.