How many times can rod and main bolts be torqued?
From ARP catalog:
Are ARP bolts and studs re-usable?Yes. As long as the fasteners have been installed and torqued correctly, and show no visible signs of damage, they can be re-used. If they show any signs of thread galling or corrosion, they should be replaced. In the case of rod bolts, if any of them have taken a permanent set and have stretched by .001 or longer, you should replace them immediately. See page 29 in the catalog for more detailed information on this critical measurement.
Here's page 29:
http://arpcatalog.com/?src=home#29/z
I don't totally agree with their write up.
They recommend throwing away a bolt that has a .001" of permanent stretch. EVERY BOLT GETS .001" OF STRETCH WHEN TORQUED PROPERLY.
Their way of measuring bolt stretch is not accurate. They say to use a "bolt stretch" gauge when you tighten the bolt/nut. this method also gives elastic and plastic deformation. Elastic deformation will go back when the load is taken off. Plastic deformation is permanent stretch and can only be measured when the bolt is not tightened, before you tighten it, and then after it has been loosened. You can't determine the amount of plastic deformation by measuring the bolt length under load.
When I did my bolt stretch studies, I brought the rod bolts to the tool room to be ground and centered. This is where they GRIND the ends flat and parallel and drill center holes exactly in the center of the head and tip of the bolt. Then I would etch numbers in the bolts and measure them with ball micrometers. You have to use ball mic's as calipers are not accurate enough - ask M. Koppesser (he didn't listen to me and had to do his test over).
Then take them to the rod machining line and get them loaded in some rods and follow them to the end of the line. After they are finished, then I would loosen the nuts and re-measure the bolt length with ball micrometers (ball mic's). This will give you the accurate permanent deformation.
I would then have pistons pinned to the rods and then install the pistons in engines and send them through the dedicated torque multiples and record the data from the multiple for torque and angle. Then remove the pistons from the engine, and measure the bolts again with ball mic's.
I have done bolt stretch test, and worked with the industry experts to set up the equipment needed to torque the rod bolts properly. I am not just some "internet jockey" throwing bull ****.....