Part 6 - Factory GM Connecting Rod Machining and Rod Bolt Install -In Depth Performance Engine Build 620+ Horse Power Street/Strip Pump Gas 454 Big Block Chevy Rod Bolts - ARP part# 135-6002
Torquing bolts and nuts together knocks burrs off of the threads of both the nut and bolt. After knocking off those burrs, the torque values get more consistent and repeatable. ARP bolts are cold rolled and are not as bad as most other bolts, because this process tears up the threads less and results in a very consistent finish - providing the tool is very clean. However, the nut threads are still cut using tooling that still causes burrs. This makes it necessary to torque the bolts multiple times, so that you get a consistent stretch on the rod bolt. I have found that when tapping bolt holes in blocks, or torquing any other fastener - that you get the most consistent results with torquing the fasteners three times. It probably isn't necessary on an ARP fastener though, because they take a lot more care when manufacturing their items - two is probably sufficient. In the engineering world when we are doing iterative analysis of a problem or using limits, often we get the most optimal result when we go through the process three times - that will get you within 90 percent of a correct answer. You may find it is similar to when a port stops flowing air, even when you increase valve lift. There isn't any point to adding more lift, it won't get you any better result unless you do more work on the head.
Torquing the rod nuts then loosening then retorquing them Burnishes the nuts and creates a pattern for the rod nut so you get a more consistent clamp load on the fastener fwiw
You pre balanced the rods but then took all the caps off and didn't seem to keep them matched. It doesn't matter since you ground the mating surfaces but doesn't that throw the balance off slightly?
