Due to inconsistencies in friction with oil, moly, and other lubricants, multiple cycles of torqueing the bolt, loosening it, and then tightening it again are required to achieve the necessary preload or stretch.
When a fastener is initially tightened, the friction is at its highest level while the preload value or stretch remains low.
As the fastener undergoes numerous cycles, the friction decreases and the preload increases.
This occurrence is referred to as 'preload scatter.' With ARP Ultra Torque assembly lubricant, a fastener needs to be torqued only once to reach within 5 percent of the ideal preload, and it stays consistent through all following cycles, from race-prep machining to final assembly.
Additionally, due to the inconsistencies found in standard lubricants, it is possible for adjacent head bolts or studs to exhibit significantly different preloads.
This scatter can result in bore distortion, hinder piston ring seal, and lead to inadequate head gasket sealing.
