1-) Part Number: ARP - 247-4201
Pro series cylinder head studs from ARP are cold-forged to ensure molecular integrity. They are heat-treated prior to thread rolling and machining and are rated at a whopping 220,000 psi. ARP Pro series kits are also available with 12-point nuts, and all kits come complete with hardened parallel washers for an even load distribution and accurate torque readings.
2-) Part Number: ARP - 100-9910
Because of frictional inconsistencies with oil, moly, and other lubricants it takes multiple cycles of torquing the bolt, loosening it, and tightening it again to obtain the required preload or stretch. Typically, when a fastener is first tightened, friction is at its highest point and the preload value or stretch is low. As the fastener is cycled numerous times the friction decreases and the preload increases. This phenomenon is called "preload scatter." With this ARP Ultra Torque assembly lubricant, a fastener need only be torqued once to get within 5 percent of ideal preload, and it remains consistent through all subsequent cycles (from race-prep machining through final assembly). Moreover, given the inconsistencies of ordinary lubes, it is quite possible for adjacent head bolts or studs to have vastly different preloads. This scatter causes bore distortion, hampers piston ring seal, and leads to poor head gasket sealing.