ARP Studs (11 mm) Torque confusion

[sparkoid]

So after multiple block thread failures while torquing head bolts on my 11 mm block,  I've finished drilling/tapping for time serts.  I have a set of 11 mm ARP studs in hand.  These are the 204-4701 kit mentioned elsewhere in the forum.  Note that while the studs fit, they are spec'd by ARP as for an '82 1.8 (gasser?); ARP says they do not have a kit for *11 mm* 1.6's (?!?).  So I'm reluctant to use their torque spec on my block.

I noticed my threaded block holes are ~ 32mm deep, even though the stock bolts only engage ~12 mm of threads. The studs will do ~20 mm if I leave minimal extra threads above the nut, and my theory is more threads in the block = less stress per thread.  So I'm waiting on some 22mm inserts to show up rather than use the 16's that came with the kit.

What's confusing is the torque spec that came with the studs.  ARP sez to torque to 80 ft lbs (in 3 equal steps). My Bentley only gets to 66 ft lbs.  Given the well known fragility of the 11 mm blocks, I don't want to risk over-torquing yet again!

I realize the lube they send with the kit is supposed to reduce the thread friction which will result in a lower clamping force for a given torque, but I'm on the time-sert / studs path because I've already had (block) thread failures and don't want any more.  The engine is normally aspirated, bone stock.  If I do anything special, it would be a Giles pump, and only if the stud thing works.

Anyone out there do the 11 mm studs?  On time-serts?  Any wisdom will be deeply appreciated.

[rodpaslow]

If using ARP you cannot go by what VW / bentley/ oem specs.  ARP are not stretch bolts like OEM.  With 11 block, I don't know if I would go with arp - no give if you over do it.  At least oem will stretch or yeild.  ARP will not.

[monomer]

My 11mn block has those studs??? studs. Use arps torque numbers.

The first there threads see the most force. Normally tapping is 1.5x threads diameter.

[R.O.R-2.0]

If using ARP you cannot go by what VW / bentley/ oem specs.  ARP are not stretch bolts like OEM.  With 11 block, I don't know if I would go with arp - no give if you over do it.  At least oem will stretch or yeild.  ARP will not.

ARPs will just pull right out of the block..

[745 turbogreasel]

What's confusing is the torque spec that came with the studs.  ARP sez to torque to 80 ft lbs (in 3 equal steps). My Bentley only gets to 66 ft lbs.  Given the well known fragility of the 11 mm blocks, I don't want to risk over-torquing yet again!

I realize the lube they send with the kit is supposed to reduce the thread friction which will result in a lower clamping force for a given torque,

With super slippy lube, you will have less friction on the threads, providing more clamping force at a given torque value.
If the top threads are a  different pitch, that would also change things.

Don't 11MM bolts  come in stretch and non-stretch flavor? 66 sounds like a non-stretch spec.

[R.O.R-2.0]

What's confusing is the torque spec that came with the studs.  ARP sez to torque to 80 ft lbs (in 3 equal steps). My Bentley only gets to 66 ft lbs.  Given the well known fragility of the 11 mm blocks, I don't want to risk over-torquing yet again!

I realize the lube they send with the kit is supposed to reduce the thread friction which will result in a lower clamping force for a given torque,

With super slippy lube, you will have less friction on the threads, providing more clamping force at a given torque value.
If the top threads are a  different pitch, that would also change things.

Don't 11MM bolts  come in stretch and non-stretch flavor? 66 sounds like a non-stretch spec.

the 6pt bolts have a straight up torque value..

the 12pt bolts have a torque value, plus a yield value..

[sparkoid]

I should have mentioned I have the earlier 11 mm head bolts, hex head, which do not give.  At all.  I have some cute cast iron curly-cues that used to be threads to prove it.

The ARP studs in this kit are undercut, intended to provide some stretch.  How much compared to the later 11 mm head bolts, I don't know.

I won't pull the studs out of the block if I know what the appropriate torque level is to clamp down the head, for this type of fastener using this type of lube.  Sounds like I'm on virgin territory here.  The lube ARP provides alters the relationship between the torque (part of which is thread-to-thread friction) and the resulting clamping force.  Their thread pitch on the nut side is finer as well.  Guess I'll have to chat up the ARP boys some more...

[RustyCaddy]

my 11mm block with undercut ARP studs went this way.

tightened all to 30, then to 60 and then to 90 using ARP lube.  Ran the engine to warm it up.  Backed each stud off a 1/4 turn or so then back to 90.

Later got pressure in the coolant so i retorqued to 95...more pressure..retorqued to 100 and haven't had a problem since.

That said, i had good threads

[sparkoid]

Hey RustyCaddy, thanks for your reply.  

Are the numbers you quoted Newton-Meters, or foot-pounds?  Your ultimate torque of 100, if in N-M, is reasonably close to ARP's recommendation of 80 ft-lbs, (which is ~108 NM).

BTW, I stated earlier that using a thread lube lowers the clamping force for a given torque spec, that is BACKWARDS; the slicker the thread, the more turn you get till you hit a given torque, thus a HIGHER clamping force (and thread shear stress).  Which is why I posted this thread to begin with.

I have a query in to ARP's tech support, stay tuned...

[RustyCaddy]

It was ft/lbs.

Check the search when you can.  some folks have torqued ARP studs really high...i think up to 120 ft/lbs in a sound block, but that might have been 12mm.

Raceware studs seem to give people problems past 80 IIRC

[R.O.R-2.0]

It was ft/lbs.

Check the search when you can.  some folks have torqued ARP studs really high...i think up to 120 ft/lbs in a sound block, but that might have been 12mm.

Raceware studs seem to give people problems past 80 IIRC

you can go to 125+ with the real diesel studs..

[sparkoid]

R.O.R, what do you mean by "the real diesel studs"

Prior searches are what led me to ARP to begin with, but maybe it's time to troll again...

[R.O.R-2.0]

R.O.R, what do you mean by "the real diesel studs"

Prior searches are what led me to ARP to begin with, but maybe it's time to troll again...

ARP makes regular 12mm studs, and ARP2000 diesel specific 12mm studs..

AKA: real diesel studs..

[92EcoDiesel Jetta]

R.O.R, what do you mean by "the real diesel stud"
...

I thought R.O.R was referrin to himself?

[R.O.R-2.0]

R.O.R, what do you mean by "the real diesel stud"
...

I thought R.O.R was referrin to himself?

LMFAO!!!

just about fell out of my chair from laughing!!

thats pretty hilarious btw..