[wojo1963]

The formula for torque values is: T = K D F
You determine the correct torque value needed based on the preload required in the bolts to ensure mating surface contact or to lock the two threaded members so they do not back off and seperate. The standard type automotive bolts K is usually a factor of .2. This is for clean dry surfaces. If you put a lubricant on threads, the K will drop down to around .1 and you will double the preload in the bolts and between the mating surface. This will also double the stress in the bolt. Just the opposite occurs if the threads are rusty. K may double to .4 and the preload will drop in half.
If you are interested in getting more info about bolts, and will probably be as much as you will ever need go to Fastenal.com and download their fastener technical reference guide. It is about 50 pages. If you have bolted joints you do not want to fail, buy your fasteners from Fastenal . I have been buying from them for almost forty years. They are a little more expense, but you know exactly what your are getting. They own their factories. Even their overseas factories are in Taiwan not China. If you need exact certs for the material, you will get it. The exact test reports for the bolts. The hardware stores are ok for nonload bearing components.

[elefantrider]

Interesting info, will check it out. I got my grade 9 from Fatensal. Same length as factory bolt. They guy at the counter said they were discontinuing grade 9 and could give me a great blowout price. He did. I just used one little longer hardware grade 5 to pull the ropeshaft close enough to get in the grade 9s.

[TempestFugit]

I've done a bunch of them, always torque to factory specs, never had one loosen.

[elefantrider]

Thanks. Will try that next time. Hate to use Locktite because removing, it's not going to turn freely by hand until the last thread.