head studs losing their torque on 3.3 turbo
 

I assembled a 3.3 turbo motor a few years back using ARP head studs. Every 1,000 miles or so I need to re-torque the heads. When I check the torque it will be down to 10 lbs or so. The studs aren't pulled, and the heads torque down to 30lbs.
Any suggestions on how to fix this?

ARP recommends 38 ft-pounds torque using their lube. This might help.

https://tech.arp-bolts.com/instructions/204-4206.pdf



My current build is still torqued after 600 miles. its a NA engine but no problems with torque.

The initial torque was to 38 ft lbs. with their lube. When they came loose the first time, Henry @Supertec suggested 30 lbs.

Did you Loctite the studs into the case?
I presume you are using the ARP washers and flange nuts?
Did you mark the angle of the nut relative to the head by any chance?

Did you Loctite the studs into the case?
yes.
I presume you are using the ARP washers and flange nuts?
yes.
Did you mark the angle of the nut relative to the head by any chance?
no.

That all sounds good. I presume then that you have put some sort of sealing ring between the head and the cylinder flange. Is that correct?

It's an easy thing to mark the flange nut to detect loosing, but that is not very common. Happens though.

Harold, it seems like multiple builders here and two that I’ve spoken to directly recommend against using ARP headstuds for the exact reason you are experiencing. No one seems to know exactly what it is about them that is the root cause of the issue, but it’s fireside knowledge now getting passed on. It sucks you’re dealing with this!
Before you swap them out for other studs, is there enough threads showing to try to double nut them? Spitballing here but would be an interesting test... check the easy to get to ones in 500 miles and see if it helped?

Speedy Squirrel,
no sealing ring between the head the cylinder flange.
gsxrken,
I'll check to see how much thread there is. Worth a try at this point.
What head studs are folks using?

Harold,

You could also try cleaning the lube off of the nut and (possibly?) stud, then torque to 38-40 ft-lbs.

Rahl

We used 993 Turbo head studs for my race engine build. They seem to be "the" choice these days and they are, from what I am told by people that know, better than any other option out there.

I think the nuts are loosening Gumba. I hope you will do the marking exercise to confirm this before taking everything apart.

ARP makes some really nice studs, very straight, and with rolled threads. They are used to designing head studs that are tightened to much higher torques than we can handle though. On top of everything else, they use that flanged nut.

The bottom line is that the threads are super smooth, so they have low friction anyway, plus, they give you a lube that also lowers the friction. Finally, they give you a flanged nut that is also smooth. with black oxide coating for low friction.

I agree with cleaning the oil off the threads, plus switching to a non-flanged nut.

So the first suggestion is to:
clean off the threads
switch to a non flanged nut
torque to 38-40 lbs.
any lube on the threads?
Since the heads & cylinders have come loose, should I assume they will re-seal when I do the above procedure?

Second choice is to disassemble and replace with 993 studs. The current part number is:
993-101-170-54, fully threaded dilivar stud. Can someone confirm this number.

I agree. I won't use anything else. I think Porsche figured that rolling the entire stud closed up the grain boundary defects at the surface that were leading to inter granular corrosion, and ultimately, failure. Just guessing. They work though.

I believe one of the other suggestions is to scuff the washer surface so there is more friction between the nut and washer.

john

That is the correct part number.

https://www.pelicanparts.com/More_Info/99310117054.htm?pn=993-101-170-54-OEM

They will probably reseal. There is no gasket or anything like that.

v e r t e x has them for $40/stud vs $57 on pelican

I'll try the first suggestion. This is in the bus, and I can actually get to all the head studs without dropping the motor. Sending the 7006 out for a few mods, so will be a few weeks before I can fire it up.
Thanks for all the suggestions.

Watching!!!

Just about ready to install ARP studs in my 3.0 build.

Thinking that I will call ARP tomorrow, see what they say

Try Loctite sleeve fit 640 instead of lube.

Supertec has the solution.

https://www.pelicanparts.com/More_Info/SPTCHSK1.htm?pn=SPTC-HSK-1&bt=Y&fs=0&SVSVSI=911M

http://forums.pelicanparts.com/uploa...1603283189.jpg