As I understand it, "torque" really relates to a measure of the degree of
resistance or friction. The goal is to stretch the bolt to about 75% of its
capacity. But since we cannot actually measure the stretch itself, it is
related to the amount of torque necessary to acheive this degree of stretch.
Since different lubes effect the degree of resistance, that subsequently
effects that actual torque number used. For moly lube, the torque should be
60-65ft lbs. ARP was not sure what a synthetic oil torque would be, but it
would be less than regular oil. Using regular 30 weight oil they suggest 80ft
lbs. Based on my experience (now), synthetic oil should be less... probably
70lbs. I did a torque to 70 before going to 80 without problem. I broke the
4th bolt of my final 80lb torque sequence. However, the first 3 bolts, though
they took the 80lbs, may very well be over torqued (or stretched) and weak
now, so I replaced them all to be sure. Now the my brain is working again, I
clearly remember using moly lube and 60lbs the other 3 times I torqued these
bolts, always without problem. That will teach me to make sure I write this
stuff down!
Greg
-- "John F Sandhoff" <sandhoff@csus.edu> wrote:
[off-list]
> ...seems that I did over torque the bolt due to the synthetic oil...
So, I'm curious... the type of oil (dino vs synthetic) affects the
desired torque? I can see oil vs no oil changing things, but I
hadn't realized synthetic was that much slipperier - interesting...
-- John
John F Sandhoff sandhoff@csus.edu Sacramento, CA
|