Nut will not hold torque.

[vping]

l'm having a set of pistons pressed on and having them balanced. Machinist tells me the nuts/bolts will no hold torque. May be an odd question but what does that mean? Im buildind another that is not balanced and even though I'm torquing them how do you tell? He replaced the nuts and gave me the old one to toss.
He also told me the rod bolts and main studs/nuts are some strong stuff so keep them.

 

[Hap Waldrop]

For starters, what connecting rods are we talking about, I assuming MGB, so eiter early angled or later straight rods, you mention press fitting, so I'm thinking later 18V MGB rods . Early angled MGB rods have 3/8" bolts that thread right into the rod itself, they torque at 45 ft lbs, so if that style you always got to make sure it not the threads bad in the rods, if so, that when the rod becomes a paper weight If they are later straight rods, either the floating or press pin style, then they use 11/32" bolt and nut arrangement, and only take 35 ft pounds of torque, oil or lubed threads on either style when torquing. If the machinist told you the bolts will not hold torque, they probably been overtorqued before , quite possibly to the earlier 3/8" rod's spec, it happens, if so then, yes it was time for new rods bolts, which is something I always do anyway on engine rebuilds. Hope this helps.

 

[vping]

Yes and no. this place has been there for at least 30years and has customers lined up out the door getting work done. Do I trust the nuts are in question which is why he replaced them or do I get new? These are press fit 18v. He told me the bolts are as good as arp and that "old english stuff was over designed for its day"

 

[Hap Waldrop]

Vince , it all depends on if they were made for the MGB application, as far as I know only ARP and the normal Brit parts offer MGB rod bolts, now the early rods, it just a common bolt, but on the later MGB rod and nut application, it's all about the rod bolt head design, and how it fit into the rod in that area, some 1275 racers use big block Chevy rod bolts and they can work and aore cheaper, but if instlled wrong it can be a nightmare. I'm sure your guy is good, and hopefuly whatever he used clears the camsahft and sits inthe rod correctly as for head design, thread legth and all other matters. In the future I would just supply the machinist with new ARP rod bolts and be done with it.