Torquing head studs

[Green79]

No reply from ARP today, but I did find generic torque specs on their website. It specifies 60 ft-lb for 10mm studs, and 71 ft-lb for 11mm studs (and 86 ft-lb for 12 mm studs)- all with ARP moly lube.

Look here:


So they put the wrong spec sheet in the box... well, I'll torque them to 71 now and hopefully everything will be fine. It hasn't leaked yet, so if I go tighter I expect it'll stay leak free.

[lord_verminaard]

Notice the Red print: "The torque values represented here are intended to be for general information, not for specific installations."

I heard that the TDI guys using ARP studs were actually using a Ford Cosworth application.  They experienced failures of head gaskets and were blaming ARP hardware, however I suspect that they were not torquing them down enough.  If it were me, I'd probably torque it at least 20% more, as a TDI at 25 psi is way more cylinder pressure than any Cosworth engine will ever see.  

Brendan

[Green79]

Okay, new info:

I traded a couple emails with Paul at ARP. He did confirm that the wrong specs were sent with my studs. He says the torque for 204-4203 11mm studs for VW applications is 80 ft-lb with moly lube, or 85 with 30 wt motor oil.

However, this does NOT apply to diesels. He said they don't have info for this application. And yes, the info in the above chart is only a general guideline.

As for me, I'm going to torque mine from 60 up to 80 and leave it at that.

[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".


Chris

So in the light of new information straight from the  horses mouth so to speak, do you wish to change any part of the above statement? Or are you feeling lucky pabst? :lol:

[VW_Commuter]

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".


Chris

So in the light of new information straight from the  horses mouth so to speak, do you wish to change any part of the above statement? Or are you feeling lucky pabst? :lol:

Wow, talk about throwing gas on a fire  

[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".


Chris

So in the light of new information straight from the  horses mouth so to speak, do you wish to change any part of the above statement? Or are you feeling lucky pabst? :lol:

Wow, talk about throwing gas on a fire  

Ha, now that's funny cus I forgot I'm lurking 4000 miles from home and I was thinking how'd ya do that? 'course  -4000miles, and over here we say "don't put petrol on  a fire"... I was struggling with the image of methane.... :mrgreen:

[Luckypabst]

No I don't want to change anything that I said. Study fasteners and the properties of metals before "throwing gas on the fire".

I'm not here to argue with ARP or anyone else - their engineers (not their salespeople) design and spec their hardware to meet a balance between performance, reliability and liability.

Anyhow, my beef was with all the debate about how to torque ARP studs. My answer was to follow the directions and you kept pressing me for more information. Again I say don't deviate from what the ARP engineers spec out for their fasteners - there should be NO QUESTION as to how to attach a cylinder head to a block using ARP studs. If you keep blowing the gasket then it's time to step up a bit - look at their chart posted above, they offer studs in 220,000 psi in the same diameter which would be a viable improvement over the 190k studs that everyone is using.

Tell me how the new information is in contrast to what I said, anyhow? 75% of yield is the same regardless of the engine.


Chris

[clbanman]

I think there is a bit of misunderstanding of how torque values are specified.   In a very simplified form, there are two considerations:
   
Max torque for the stud material.  Every stud or bolt has a maximum torque that is determined by the material, size, etc.  If you go beyond this torque value, you can enter the permanent deformation range and you have permanently damaged  and weakened the fastener.  If you go too far, you will actually break the fastener.

Application torque is determined by the engineer based on a desired clamping force.  This value can possibly be far below the max torque for the fastener.   In the vast majority of cases this is the value you will find specified by the OEM of the engine, etc.  A fastener does not have to be torqued to the maximum possible value to achieve the desired clamping force between two surfaces.  

For a head fastener application, if you exceed the basic torque required to achieve the desired clamping force, you risk getting into a range where you can distort the block/head interface beyond what the entire system has been designed for.  How much distortion you get and what effect it has on the life depends on far too many variables for me to get into.  In most cases if a fastener is bought on strictly a size specification, the fastener manufacturer will give you a max torque for the stud itself.  It is only when the fastener is purchased with a specific application in mind that they may provide a application torque.   If using studs which are not TTY (torque to yield), don't follow the OEM recommendation for torque value plus X degrees of rotation.  This type of value is specifically for TTY fasteners and you will get very different clamping forces if you do this on a non-yielding, permanent stud.

[Green79]

So I re-torqued the studs today. I started off with a re-torque at 60 ft-lb, and all of them took around 1/8 turn to get back to 60... so it certainly seems that, regardless of what torque you decide on, a re-torque should be done.

After that, I went to 70 on each,  then 80 ft-lb on each one, and they all tightened up nicely. Bolt #6 seemed to take a bit more to get to 80 ft-lb., but not enough to make me worry.

[VW_Commuter]

I just got a reply from Zac at ARP concerning the torque value to use and he said:

The torque value given is specified more towards the diameter of the stud, the material of the stud and what it is being used for (i.e. cylinder head studs) and not the specific vehicle application. We use that torque specification for all head stud kits where the stud is 12mm and has a tensile strength of 200,000 PSI.

I'm not sure what the pre-load or clamping force is but since I'm not planning on boosting above 15psi right now I'm just going to torque mine to 86ft. lbs. with a Victor Reinz gasket and see how it goes.

[Luckypabst]

Good info - thank you Greg!
Chris

[vwt4]

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

Can anyone confirm the 'best' procedure to use on my 1.9TD ABL engine head bolts please?

Just fitted a new head,
have torqued the bolts (new ones of course) to recommended torque on Autodata and used the right pattern etc

Should I run the van through a few heatcycles and retorque them? should I tweak them when the engine is hot? (surely thats a bad idea>!!)

Having (hopefully unrelated) issues with cam cover gasket leaking at the front although the head gasket seems to be ok....no mayonnaise in the oil, coolant level ok, however I have only had it running today and not driven yet as still testing things.

All advice appreciated