Torquing head studs

[53 willys]

IMHO...if your using a fiber gasket you should retorque NO MATTER WHAT!! weather your using studs or bolts...
I think if your gonna run fiber gaskets then you should warm up the engine WITHOUT the cooling system cap on(no pressure) then let it cool and retorque to 80ftlbs....if your running MLS & studs then clamp the bugger and go...
my.02

[zukgod1]

That's what I've done the last 2 times and been fine so far.

[overdrivegear]

What is the ARP torque spec for 11mm head studs?  Is it the same for the 12mm at 80 ft.lb?

[rallydiesel]

I have ARP's and used the normal pattern and torqued to 80 ft lbs. and then to 100 ft lbs. after a warm up.

you running the stock fiber gasket??
what kinda boost numbers are you pushing??

I have the MLS gasket and am running stock boost - for now.

[Luckypabst]

Stretch bolts or studs can indeed stretch under load, causing sealing problems.
That's why I wasn't content with ARPs and instead went for custom studs.

ARPs are not "stretch" studs.

I'm confused about all this head stud quandary. There should be no debate or variation - just follow the manufacturer's specification, e.g. 80 ft-lbs for ARP 12mm studs with ARP lube and a retorque after one heat/cool cycle.

Fastener torque is a function of material composition, diameter and thread pitch.

Chris

Surely you mean fastner 'strength' is a function of your variables...

Torque is function of the job you wish to accomplish isn't it :?: ....

I meant what I said but could have elaborated a bit more. The engineered torque spec for a given piece of hardware is a function of the above properties - it's not a value or procedure than can be applied at random or on a whim to fasteners of varying design.

And yes, a re-torque is far more important with fiber gaskets after a heat/cool cycle since the gasket will compress as the block and head expand when heated, then retain the compressed state upon cooling. My steel gasket still allowed an additional 1/8 turn up to 80 ft-lbs after the first cool-down. Just standard procedure for the most part.

Chris

[Mark(The Miser)UK]

"Fastener torque is a function of material composition, diameter and thread pitch.

Chris"

I guess you missed off  the words 'spec' or 'max' and maybe 'applied'  :wink:  

Aren't these studs universal... in that I assume they might  be used in other engines after all VW doesn't have a patent on 12mm studs; so that the same stud will likely have a slip of paper carrying different tightening spec, for a different engine or are all heads clamped the same?
So do you know how much a fibre gasket collapses under the specified torque? It clearly does because of the perimeter of the gasket shows a ridge , .I've tried measuring andn old gasket but I suspect the edge of the gasket exposed to the weather swells beyond it's original thickness.

Part of my research into this topic is because all the aftermarket gaskets I see on ebay seem to have different hole/notch arrangements depending on the manufacturer. I'm just not willing to pay for stealership  prices, which would of couse [presumably] make life easier but means I pay the same for a gasket as I did for the car:roll:

[Green79]

I need to double check, but the 11mm ARP studs I just installed in my 1.5 came with instructions that said to torque to 60 ft-lb. I only have ~60 miles on the rebuild, but it sounds like I could do an additional torque to 80 ft-lb after a couple hundred more miles and then call it good? Or should I do it sooner rather than later?

For what it's worth, I'm not losing any coolant or oil at all so far... but I'm seeing oil pressures well in excess of 100 psi (pegged to the back side of the stop in my mechanical 100 psi gauge) when cold, measured at the head. Once warmed up, it gets up to 100psi when floored still, but at idle it's around 30 psi.

[53 willys]

I need to double check, but the 11mm ARP studs I just installed in my 1.5 came with instructions that said to torque to 60 ft-lb. I only have ~60 miles on the rebuild, but it sounds like I could do an additional torque to 80 ft-lb after a couple hundred more miles and then call it good? Or should I do it sooner rather than later?

For what it's worth, I'm not losing any coolant or oil at all so far... but I'm seeing oil pressures well in excess of 100 psi (pegged to the back side of the stop in my mechanical 100 psi gauge) when cold, measured at the head. Once warmed up, it gets up to 100psi when floored still, but at idle it's around 30 psi.

if I was you I would do a re-torque SOON..but I don't know about what FTlbs to go to?? I know for sure my 12mm ARP's said 80FTlbs..11mm studs may only be rated for a 60ftlbs torque so maybe you can go 65-70 if you want a over torque? yes? no?

your oil psi sounds normal to me...you reading at the head or oil filter flange??

[AudiVWguy]

ARP  1-800-826-3045

[Luckypabst]

"Aren't these studs universal... in that I assume they might  be used in other engines after all VW doesn't have a patent on 12mm studs; so that the same stud will likely have a slip of paper carrying different tightening spec, for a different engine or are all heads clamped the same?
[/color]

Fastener torque is the same across the board, regardless of the engine design/brand/etc. As I said, the torque spec is a function of the fastener design, not the engine design. The fastener will break long before "crushing" the head or pulling *undamaged* threads from the block. The slip of paper says "80 ft-lbs with ARP lube".

I need to double check, but the 11mm ARP studs I just installed in my 1.5 came with instructions that said to torque to 60 ft-lb. I only have ~60 miles on the rebuild, but it sounds like I could do an additional torque to 80 ft-lb

Then 60 ft-lbs would be the spec for 11mm studs. Don't overtorque to 80 ft-lbs.

Chris

[Mark(The Miser)UK]

Fastener torque is the same across the board, regardless of the engine design/brand/etc. As I said, the torque spec is a function of the fastener design, not the engine design. The fastener will break long before "crushing" the head or pulling *undamaged* threads from the block. The slip of paper says "80 ft-lbs with ARP lube".
Then 60 ft-lbs would be the spec for 11mm studs. Don't overtorque to 80 ft-lbs.

Chris

This is interesting, so although the studs are obviously stronger than the stretch bolts they are not as strong as their threads, nor the block threads for that matter. So is the 80lb ft spec taking into account non standard boost , like some of the racer types that run nearly 30psi??
Anyone know the alloy, or simply breaking strength of a stud?

[Luckypabst]

The engineers have calculated that at 80 ft-lbs with ARP lube (120 ft-lbs with 30 wt), the studs will then be loaded to something like 142,000* psi for that thread pitch (1.75?).

The given torque value is designed to draw the stud to a specific percentage of the yield point for that fastener's material. So with a design load of 75%, the yield point is 190,000 psi.*

If extreme boost is causing head gasket failures, it will be because the head is deforming between the studs which is not uncommon as I understand. I can't imagine that ARP would recommend to exceed their engineered torque value for any reason - this would be the time to step up to the next larger stud diameter (I'm not saying this is even possible).

I do remember there being a general rule of thumb stating that a certain ratio of thread depth to fastener diameter would result in the threads being stronger than the fastener. With the 12mm ARP studs threading to a depth near 2x the diameter, the threads that are cut into the deck surface will be more than strong enough as long as they aren't damaged in any way. This depth to diameter ratio would obviously change with fastener material and minor diameter and even the thread form so this would require some research to be accurate.

Edit: I don't recall if the ARPs neck down between the threaded ends but I bet they do. If not, the likely failure point will be in the minor diameter of the coarser threads, just above where they enter the deck threads. Otherwise the studs would ultimately fail at some point along the smallest diameter, assuming no other defects exist.

* - edited again using VW_Commuter's values.

Chris

[VW_Commuter]

Looking at my new set of ARP headstuds, part no. 251-4701, the installation instructions say the yield strength of the studs is 190,000psi.  The instructions also state

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 80ft. lbs. for ARP MOLY ASSEMBLY LUBRICANT (or ARP THREAD SEALER) or torque the nuts to 120ft. lbs. with 30wt. motor oil.

If someone wants I can scan the instructions and post them as a jpg.

[Turbinepowered]

I need to double check, but the 11mm ARP studs I just installed in my 1.5 came with instructions that said to torque to 60 ft-lb. I only have ~60 miles on the rebuild, but it sounds like I could do an additional torque to 80 ft-lb after a couple hundred more miles and then call it good? Or should I do it sooner rather than later?

Recommended torque on the undercut 11mm ARP studs, from the slip I just pulled out of the box (Part # 204-4701), is 70ft-lbs with the ARP lube, 85 ft-lbs with 30w motor oil. It is recommended that "Due to the expansion rate of aluminum, it is recommended that the torque should be 65 ft-lbs" with the ARP moly lube.

[Green79]

So I'm looking at the instructions that came with my 11mm heads studs- ARP part number 204-4203.

The instructions clearly state to torque the nuts to 60 ft-lb when using the ARP moly lube. There is no value given for use with 30-wt motor oil (the instructions say motor oil is not recommended).

HOWEVER... at the top of the instruction sheet, next to the stated strength value of 190 ksi, it says "10mm"... so I think they put the wrong spec sheet in the box.

Does anyone have the actual spec sheet for 204-4203 studs? I'm going to email ARP of course, but if anyone has it here first, it would be appreciated if you could enlighten us with the proper values.