ARP Head/Cylinder stud torque?

[STROSEK]

I'm in the middle of my 964 rebuild and need some advise... What is the correct torque spec for ARP head/cylinder stud bolts?
The back of the ARP box has one thing, Waynes rebuild book has another and my 993 factory manual has something totally different. They all can't be right!!

If someone could give me the exact torque specs for this application it would be appreciated.

Thanks in advance.

[sms1305]

You need to make sure that you have the right instructions for the kit that you have. Looking at the ARP catalogue, there are two kits for 911s. I have #204-4206 (911 and 930 turbo). The other kit that I see is #204-4210 (996).

Here's the instructions on my sheet for the 4206:

QUOTE:
(3) If cylinder head studs protrude into blind hold, lubricate the threads, nuts & wahsers with ARP MOLY ASSEMBLY LUBRICANT.

NOTE: Loctite may be used if a permanent mounting of the studs is prefered. The fasteners, however, must be torqued prior to the loctite setting up.

(4) Install cylinder heads and check for binding or misalignment.

(5) ARP recommends using the ARP MOLY LUBRICANT or at hte very least, a good quality Moly Lubricant as opposed to motor oil. This is due to higher friction on the studs as well as inconsistencies in the clamping force of the fasteners when motor oil (or low quality lubricant) is used.

PRELOAD (TORQUE) RECOMMENDATIONS:
Torque values are based on 75% of the fasteners yield strength. Use the manufacturers torque sequence but do not use the engine manufacturers torque specs. Torque the nuts to 38ft. lbs with ARP MOLY ASSEMBLY LUBRICANT
Note: Do not use any other Moly Lube. Use only ARP MOLY LUBE or head gasket failure can result.
END QUOTE

I'm still trying to determine whether the height is 135 mm or 132 mm as the book states.

I don't know if the same instructions apply if you're using the 4210 kit.

Good luck!!

[sms1305]

I just spoke to an ARP tech rep. He said that you must reach final torque within the time specified, which means you need to install the piston, cylinder and head within 30 minutes of installing the studs.

No one has ever mentioned this that I've seen, but it seems like it will be a real race to get everything done in time before the loctite sets.

Does this make sense?

[Eagledriver]

No it doesn't make sense. I suspect the 30 min thing is for using locktite. I don't have experience with these studs but I would be worried that 38 ft/lbs is too much for the case and heads to take. The heads could be distorted or the studs could pull from the case. I don't know the right answer these are just my thoughts. Hopefully someone more qualified like Steve or Henry will help.

-Andy

[Jeff Alton]

So, how do you torque the nuts when you rebuild a motor with ARP studs, pull them all out and do the rat race againg installing everything?

Cheers

[STROSEK]

I used 32 Lbs and am done with it. It's a little more then Waynes book calls for and a little less then ARP calls for on the box. I'm sure it will be just fine. Fingers crossed!

Thanks to everyone who replied.

[sms1305]

Hey, good luck.

I was wondering what, if any, loctite you used on the bottom threads?

Did you assemble all the studs before installing the cylinders and heads or did you go one at a time?

[ChrisBennet]

The torque on a fastener is a function of the fastener being used - don't go by what Wayne's book or the factory manual says for a "similar" fastener. This time you will probably be OK but in the future do not use the reasoning that you used to come up with your compromise torque - follow the fastener manufacturer's instructions.

The manufacturer is trying to produce a specific tension/bolt stretch in their fastener. Simple torque or torque angle is a crude way of obtaining that tension.

BTW: Raceware head studs are also put in without Loctite.

-Chris

[STROSEK]

I did use locktite red on the studs, the case side not the head bolts... Do you think I should re-torque them to 36 lbs? I don't think it's too late? I had read that someone had pulled the studs out using too much torque and another post saying that 32 to 34 was about right with the ARP and that the ARP recommended amount was a bit high.

Re-torque from 32 to 36 or leave it?

Thanks!!

[Jeff Alton]

I would retorgue to the number that ARP supplied. Like Chris said, the torque spec is about stretch or tension on the stud. I would use their figures.

That is what I did when I installed the ARP studs on my motor....

Cheers

[sms1305]

Do you guys have any thoughts about using loctite on the ARP head studs with timecerts? The instructions indicate that they can go in with or without, but that if you do use loctite that you need to get to final torque within 30 minutes. When I talked ARP the tech guy said that that meant I would need to assemble the cylinders and heads and get final torque on the nut since there's no torque for just the stud.

p.s. I'm the guy with the two pulled studs from the last top end build. I did use loctite, but definitely did not torque the heads within 30 minutes.

Thanks.

[sms1305]

Originally posted by sms1305
Do you guys have any thoughts about using loctite on the ARP head studs with timecerts? The instructions indicate that they can go in with or without, but that if you do use loctite that you need to get to final torque within 30 minutes. When I talked ARP the tech guy said that that meant I would need to assemble the cylinders and heads and get final torque on the nut since there's no torque for just the stud.

Anyone think it is necessary to get to final torque on the heads within 30 minutes (which would require assembling one cylinder at a time)?

[Walt Fricke]

Surely the short answer to this question is not to use any thread locking compound on the case end of the studs. You don't need it to get the clamping force required to keep your heads in place. And you don't need it to keep the head studs from somehow backing out of the case on their own while driving around. Just won't happen.

Now a thread locker may prevent the stud from backing out when you go to remove the head at some time in the future. But I haven't had this problem, and even if it happens it doesn't have to be a big deal - it will only happen in the context of a top end teardown and you will be able to get the stud out, remove the corroded nut, and reinstall the stud.

This is the first I've heard of a recommendation to torque a threadlocked stud within X time of application. This must be based first on the setting time of the thread locker.

But it also has to be premised on the notion that the thread locker which has set up without the stud being under tension will hold the stud deeper into the case than would otherwise be the case. And that when you torque you stretch the stud based on that depth. But as the engine undergoes heat cycles the thread locker will fail/loosen/relent/compress, and the stud will be pulled upward, which will cause it to lose some of its stretch/tension. At least that is the only thing that occurs to me which could account for caring about this thread locking issue. The Porsche shop manual doesn't say anything about this. And were it not coming from a source like ARP, I'd dismiss it, as the amount of difference has to be pretty darned small if I have guessed correctly what the concern is.

Now if they are working off of experience with Detroit V8s, and replacing head bolts with studs, it would seem fairly easy to do a stud for bolt swap in 30 minutes, especially since you could do those one at a time if you wanted. And those studs would be a lot shorter than ours, so a small length difference would mean more.

Walt Fricke

[Nitrometano]

I already purchase an ARP head studs for my 2.7 engine. I also notice today the 38 ft/lbs for torque. My engine is the magnesium case and has Timecerts inserts installed. I have the same doubt about that much torque for the headtuds. The bigges preocupation that I have is that torque will pull out the inserts. After reading this forum, I think that the correct installation for this studs are without loctite in the engine case side. I also notice that the instruccions underside the box dont tell anything about using that. An there is no stretch method for this studs like the ARP rod bolts. Please let me know if I'm correct:

Install the head studs to the case side without thread locking compound.
Use the ARP moly lube on the cylinder head nuts.
Torque the head studs to 38 ft/lbs with case inserts installed into a magnesium case?

After your people, what have been your experience with this studs? Do you get a cylinder head leaking after the installation and running a few miles whit the engine?

Do you retorque the head studs?

They pull out from the engine case?

[pharlap71]

the bentley manual says "pre torque 15 nm (11ft-lbs) then 90 degrees(1/4 turn). I am sure this is more than 38ft lbs.

[MBruns]

The stock studs for the 964/993 with the 11 ft # plus 90 deg ends up around 40 - 42 ft #, I would not put that much on a mag case.
Mike Bruns

[Walt Fricke]

Bruce Anderson, in his 911 book, says torque head studs to 25 (steel) or 29 (Dilivar) pounds/foot. That's what I have done with mag cases and with early aluminum (sandcast) cases.

Henry Schmidt specifies the following torque for his Supertec studs:

Sandcast aluminum: 30
Mag: 26
Pressure cast aluminum NA motors: 30
Aluminum turbo motors: 32-36.

Looks like 26 would work. 38 seems way too high for a mag case, time certs or not.

[3de]

FWIW, just finished installing the cam boxes and torquing head studs on a 964 C2 with Canyon steel studs. 15 ft-lb + 90 deg = 28-29 ft-lbs (11 ft-lb + 90 deg ended up being anywhere between 24-30 ft-lbs for me at least).

The workshop manual also specifies that the bearing surface of the head nut (washer if separate from the nut) be lightly lubed with the same anti seize as the stud threads.

[porschedude996]

I just a few weeks ago I torqued my ARP’s to 38ft/lbs. First 19 and then 38. Lube on threads and washer.

[Jeff Alton]

Since my reply back 2007 I have lost count of how many sets of ARP studs we have installed. 25? Always torqued to the ARP recommended torque. Just completed a 993RS motor built out to 4.1 where we used ARP studs. Not worried about it in the least.

I struggle to see why people think they should use other than the recommended torque value supplied by ARP, when all they do is engineer fasteners....

We have had ZERO issues following ARP directives in the 17 years since this thread started.

Cheers