stevesxm

bill and raylar are correct in all respects but in the simplest terms it, just so you know, it works like this. all steel stretches when stressed and when you tension any piece of hardware, that's what you are doing... stressing it. the stretch , in engineering terms is called strain. every steel has a " stress vs strain curve" you load it...it stretches. you load it some more and it stretches some more. and if you release the load it goes right back to where it was. however if you stress it too far it goes past its " elastic limit" and into a " plastic deformation stage" commonly called " yield" . at this point on the curve, the steel accepts no more load but just continues to stretch and it will NOT return to its original length when the load is released. what has happened is that the actual molecular structure of the steel has been damaged and that's the end of that. attempting add more load ( stress) just results in a a lot of stretch followed by failure. on a connecting rod bolt, the spec you are given for " torque" is supposed to be the number that with properly lubricated bolts, will stretch the steel to a design preload on that stress vs strain curve to give you the clamp load you need to hold the pieces together.

if the hardware is true " torque to yield" and it has, in fact been there, then that hardware is a throw away after a single use. but like a lot of things, that term gets thrown around so much that people and even manufacturers use it as shorthand. so the practical answer is simple... do what the manufacturer of the bolts tells you to do. he knows what he meant when he used that term. if GM says its ok to reuse the bolts w/ new nuts, then don't try to interpret the semantics, just go ahead and do it. if they say throw away the bolts after a single use, then believe them. if you buy aftermarket bolts you follow those instructions to the letter for the same reason... especially the lube part. the parasitic friction of the assy can make your torque numbers lie to you comprehensively. thats why the stretch method is absolutely the best where it is possible to use.