lanichol
09-26-2010, 05:23 PM
I was watching one of the muscle car shows this week and the topic was on tightening heads evenly and to torque specifications.
They setup a tension gauge to compare the tension to the torque wrench. Using oil or moly, the the torque was all over the place. As with tightening heads you do a first tighten, then loosen and retighten. I believe there are charts on the ARPs website with similar results.
This would be fairly important especially where you have aluminum heads against cast iron blocks as is the case in the Subaru. The Sub 2.5 has a weakness in the design where the head gasket on the #3 can fail or is the first to fail. Using the ARP may just decrease the odds of a gasket failure and I am all for decreasing problems.
ARP Ultra Torque Assembly Lubricant: Details (http://arp-bolts.com/pages/arpultratorque.shtml)
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.
They setup a tension gauge to compare the tension to the torque wrench. Using oil or moly, the the torque was all over the place. As with tightening heads you do a first tighten, then loosen and retighten. I believe there are charts on the ARPs website with similar results.
This would be fairly important especially where you have aluminum heads against cast iron blocks as is the case in the Subaru. The Sub 2.5 has a weakness in the design where the head gasket on the #3 can fail or is the first to fail. Using the ARP may just decrease the odds of a gasket failure and I am all for decreasing problems.
ARP Ultra Torque Assembly Lubricant: Details (http://arp-bolts.com/pages/arpultratorque.shtml)
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.