Scary Torquing Experience
 

Putting the engine back together with new ARP studs. Followed the manufacturer's procedure to the letter using the supplied lube on the threads and supplied washers and nuts. Did the 2 equal step torque down of the heads and cam tower. The first pass at 20 ftlbs went fine. The second step to 38 ftlbs was the scary part. Remember I had to install the new ARP studs due to the broken Divilar stud. So when I started the last pass at 38 some torqued up like you would expect. Some started turning and feeling normal and then they slipped. That was the scary part because I thought something snapped or threads stripped. Continued to turn the nuts and they all tighten down. I guess it was just the nut slipping on the washer or the washer on the head. Anyone had this experience with the ARP studs?

Did you put lube under the nut and on the washer??

You were probably experienceing some torsional wind up in the studs (they are long) and the a release of that wind up. I would re-torque them again to the 38 to capture and excess windup or embedment.

What motor are you working on? For 65 through 89 911 the spec for head studs is 23.5 ft-lb torque.

This is a 1979 930. The supplied lube from ARP was used on the washers and nuts and threads. APR states 38 ftlbs for the studs.

Could also have been light galling. Make sure you spread the lube all the way down into the thread of the stud and nut thoroughly. If you have more to go then I would recommend running the lubed nut and stud together without the head to spread it on both parts well. Then re-lube lightly and install the head and torque.

I did re-torque today. Actually some nuts moved slightly. Hopefully all is OK.

Not for ARP . . .

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/488908-arp-head-stud-torque-procedure-settings.html

Arp
 

I followed the procedure of 38ft/lbs on my 930 engine, I have been concerned with the high torque settings required by ARP, and does it put extra stress on the case boss threads

I had the same experience when torqueing my ARP studs: smooth increase in torque then a sense of release or slipping before reaching 38lbs. It does seem like an excessive amount of torque doesn't it? I performed the procedure exactly as ARP described them.

I assume you haven't had any problems since. How long ago did you install the ARP studs? Did you re-torque after the first 1000miles?

I just did a 930 with ARP studs, I didn't like that torque as well, I felt the same thing on a couple of studs, but they torqued down fine.

For my own engine I bought a set of Henry's studs.;)

Did you guys loctite the studs into the case? If not loctited, that might explaing some of the release?

The engine's not done yet so we'll see...

Yes Loctite was used on the case threads. The Loctite had even cured for several days prior to torqueing. I called the ARP rep and he said it didn't matter if you used Loctite or the included ARP thread lube as long as the studs were not installed dry.

I used thread locker on the studs. Still going back together.