ARP have finally moved off the fence and have revised torque settings for head studs. They're now saying final stage torque 70 lb/ft.
Many opinions on the web as to what should be used, but 60 lb/ft seems to be the most popular.
Any thoughts from the forum where the real experts live?!
Edit- just noticed the instructions say torque as per steps 1 - 4 and there are only 3 steps!

Inserting the stud hand tight then torquing from the top contradicts all the advice given when I was working for MoD. There it was always said that the stud insertion torque should always be greater than the nut torque so the stud becomes a rigid part of the assembly. The sliding friction in the threads and under the nuts is a significant and very variable consumer of the torque applied. Two lots of initially loose threads tightening up together aren't going to help get consistent tension across all the studs. Not to mention wind-up in the stud itself as the nut tightens up and gets enough grip on the stud to twist the bottom a bit tighter too. That wind up will relax over a few warm-up cool down cycles.

Such issues are why stretch bolts were invented. The whole point with those being that the lengthwise yield curve is long and well controlled so adding a defined extra fraction of a turn from an initial torque setting low enough that bolt to bolt variation in frictional effects don't significantly alter the starting tension. Stretch bolts grow considerably more lengthwise than a normal bolt of similar diameter but have most of the same strength in twist so they don't suffer greatly from wind-up. For the best part of a decade I used to get sent data on the various weird bolts and fasteners used in big structural jobs with integrated torque and stretch measurement capabilities. Absolute zero relevance to my job but interesting, and a bit scary in the maths. I guess you really don't want the bolts falling out of a bridge, pylon or skyscraper.

No reason why studs couldn't be effectively re-engineered into the Rover V8 for performance at least as good as the best standard stretch bolts can do. But to me that leaflet is pretty conclusive indication that ARP aren't it.

Clive

When I put my engine back together, I put the block in first and then fitted the heads once it was in place so much the same situation as you. I tried putting the studs in first then found there was too much other stuff in the way to allow me to lift the heads high enough to drop them over the studs. So I put the heads on without any studs, the same as if I was using bolts. I then put the studs in and tightened them with an Allen key. No idea how much torque I put on them, just until they didn't want to go in any further. I put the nuts on and did them all up hand tight then did a 3 stage at 30, 50 and 65 lbft as that is what most other engines with alloy heads are tightened to and I'd also seen the arguments that the recommended 80 lbft was too high (it seemed too high to me too). I don't think stud wind up is too much of a problem as the threads into the block are much courser than those on the nuts so the turning force is going to be concentrated on the finer thread particularly with the lube on the underside of the nuts.

My engine went in at 287,500 miles and I'm now showing 329,200 so 65 lbft is good enough for 41,700 miles at least with Elring gaskets.

70 lb/ft seems a little high to me too. In a new block with freshly cut threads that would probably work OK, but in a block that's been through many heat cycles and where the threads are already worn I think you'd be coming close to pulling the studs out.
65 lb/ft is a good number!
I'm using Elring as well, so hopefully can emulate your mileage.
Just need Ray to get his machinists finger out and get the heads built now...

I'm following this discussion with interest, on here and on the other side.
The two different methodes of torqueing are not comparable to eachother due to the different thread used by ARP (topside of stud).
Isn't it possible to find an engeneering educational institute that could perform a test between the two methodes as how many tonnes of pressure is involved by the two methodes, stretchbolts versus ARP. Find a block and a head on a scrapyard (or parts of it) before they go to the oven and let them perform the test.
At the same time you can find out by what force the threads give up.
As ARP has come with different advice I doubt they have records of such test.
Tony.

The biggest problem with stretch bolts is the inconsistency. A stretch bolt from one supplier may start to stretch at 30 lbft while another from a different manufacturer may not start until 40 lbft. Then there is the amount of elasticity in the bolt once it starts to stretch. A softer bolt will stretch a lot and not apply much pressure while one that is a bit harder will apply far more pressure. I have been told (by a Land Rover independent) that some of the cheaper stretch bolts have been known to snap before you get the second 90 degree turn on them. At least when you do an ARP stud up to a certain torque you know that the pressure it is exerting is going to be the same every time.

Fully agree with you. With your previous articles about this subject in mind it made me torque my stretchers only 45º on final turn ha ha.
I fact it's a shame that even original LR bolts do not guarantee the desired quality on such an important matter.

I can't really understand why there's another thread and discussion on this now?!? I asked these questions about stud torques in my engine rebuild thread and it was discussed there...

I mentioned in my thread that V8 tuner (who I got the studs from) recommended studs hand tight (I just 'nipped' them the tiniest amount with an allen key to make sure they were seated home), and then the nuts done up to 70lb/ft, done up in 3 stages, with a rest period of 20-30minutes between stages.

Mark, YOU yourself said in my thread that "70lb/ft sounds like a good number to go for" I was taking the advice from the collective wisdom of the forum, as I'd never built an engine before... but now you're contradicting that and questioning a) ARP and their updated instructions, b) V8 tuner who told me 70lb/ft when I bought the studs, and c) yourself who agreed with it in my thread... but when it comes to your engine, it "might be a bit too tight, 65lb/ft is a good number"

Incidentally my engine seems to be running just fine at 70lb/ft..

With the amount of advice you input into my thread, I thought you were an expert at engines and these things, but it seems like when it comes to your own one there's indecision and second guessing at every turn.

Thanks for the feedback Marty.
An expert? That's not for me to say, but I am a trained and qualified engineer and have built/ rebuilt many engines over the years, including Rover V8s but never a P38 4.6. Second guessing and indecision on my own? Possibly- it's different to a customer engine 'cos there's a kind of emotional investment when it's your own, a bit like Doctors not treating and diagnosing their own family and friends.
Just looked back at the original discussion around your stud torques, at the time the ARP instructions (which I linked to in Nov 16, the one's currently available on that link were updated in December 16) gave a higher figure. Can't remember what it was off-hand. Up in the 80s? Anyway V8Devs via Gilbertd and V8Tuner via yourself said 70 and I agreed. They're the commercial RV8 tuned engine builders after all and I don't think I gave bad advice by agreeing with what they said. Gilbertd does say above that he decided on 65 for his build even after all that.
I raised the post because I'd forgotten we'd gone into any details on your build thread. I probably post too much on here just 'cos it's just a pub forum where people can just chat about the P38 and I like that and do it.
I'm sorry that my post irritated you, but thanks for taking the time to respond