Torquing head studs

[overdrivegear]

So what is the torquing procedure/values for using 11mm head studs?  I understand that there is some grey area here and that some have used their own variations.

[79rabbit4dr]

i'm about to do a HG so i've been reading up, seems like most ppl use the value's from the manufacturer of the studs (arp, etc) instead of the bentley/oem values... but you're right, it kinda seems to be a gray area.

wait, are you using oem 11mm bolts or aftermarket studs?

[VWCaddy]

I used Raceware stubs (12mm) on my 1.9D engine and torqued them to the Raceware specs of 3 steps, 20-35-50 ft.lbs. then a retorque to 50 after running the engine to temperature.

[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.

[53 willys]

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??

[kaneb]

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??

Im wondering this too.

[Mark(The Miser)UK]

I have some questions for you 'stud lovers'

1) Does ARP and Racewear use the same thread pitch on the nuts?
How does it compare with the block/bolt pitch?

2) Is it 25% or more finer? If so then can the heads be overtorqued? :shock:

3) When looking at a freshly removed head, I find that there are markings on the head from the gasket steel edges; so is that general abrading from heating and cooling of the head shuffling it around, or is it because the gasket has penetrated the head during the torquing process? :?

4) From my  set of measured results when torquing stretch bolts recently. Initial plastic stage began at about 115 lb ft, then on the later retorque stage seemed less at a little under 100 lb ft. Why did the Germans settle on this peak? :?

5) After the 1000km run what has 'given' to allow bolt releasing at some 50 lb ft? head, bolt, or gasket?... Or has the bolt simply loosened? :?
 [I know the releasing of the bolt was an old technique but I wanted the data, and I also wanted to avoid those gut wrenching snatches that some bolts undergo when overcoming their initial friction].
As I was retorquing to measured yield point only, be it 90 deg or as it happens around 45 deg;  any further turning is a waste of stretch IMO :roll: :idea:  
6000 miles  on no leaks.

6) How much does a gasket give? Metric or imperial readings welcome. Does the quoted 1.4, 1.5 ,1.6 refer to the final settled thickness?
A 2 notch mech gasket I removed [blown] seemed to measure between 1.6 and 1.7mm at the rings some 30000 miles on... Seems like a spare replacement gasket I've bought is no thicker :?

Any thoughts anyone? :?:

[Turbinepowered]

I have some questions for you 'stud lovers'

1) Does ARP and Racewear use the same thread pitch on the nuts?
How does it compare with the block/bolt pitch?

As I recall, the thread pitch on my ARP studs was the same on both ends.

3) When looking at a freshly removed head, I find that there are markings on the head from the gasket steel edges; so is that general abrading from heating and cooling of the head shuffling it around, or is it because the gasket has penetrated the head during the torquing process? :?

I'd say there would be an easy way to check this out. Clean up a head, clean up a block, throw a new gasket in there (Any size would do) and torque away.

Let it set for a bit, then take the head back off and check for your marks. For the record, when I redid the headgasket on the 1.5 in the Fox, and the 1.6TD I pulled a head from (Already studded :shock:), I didn't find ridges or marks beyond some discoloration from the gasket. I did, however, find a good amount of deposit on the 1.5 head in a ring that was just inside the fire rings in the headgasket.

[53 willys]

ARP studs are not the same thread pitch on both ends...one is definitely more course then the other..

[Mark(The Miser)UK]

ARP studs are not the same thread pitch on both ends...one is definitely more course then the other..

Interesting, so if there is a minimum torque required, and a maximum to be avoided, then ARP's at least, require less torque for same clamping force; a 1/3 less or so, depending on the thread pitch...

I wonder if stretch bolts can actually stretch under load?
If pressure in a cylinder reaches 1000psi, then that's 6000lb thrust per cylinder :shock: or 1500 on each of 4 surrounding head bolts, or am I losing it :roll: ?
I guess it depends on the flexibility of  a head :? so maybe it's 2/3 of that for the immediate bolts and a 1/3 of the force beyond.

What's the stretch force in a bolt? Are they1.5mm pitch?
Once stretched seem to carry on elongating @ or around 100lb ft.
 I can't quite work it out in my head, but here's a guess; 305mm x 2PI /1.5... :oops: Heck that looks like nearly 1200lb to stretch. I guess I'll have to dig out my Victorian maths books  :roll:

[Luckypabst]

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

[TurboJ]

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.

[Mark(The Miser)UK]

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 :?: ....

One of the aims of this thrashing out  is to understand  why head gaskets fail.
Also is warpage solely down to excessive heat and overloading, or also is actual distortion down to over zealous torquing.
I have a tendancy to under torque bolts, that is to say, do less than recomended, [where I think appropriate that is :oops: ]  
Head gaskets deteriate,and  fail after time too, but I'm wondering if extra care in attaching the head to the block increases the chance of reusing the head post gasket failure...

[jtanguay]

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 :?: ....

One of the aims of this thrashing out  is to understand  why head gaskets fail.
Also is warpage solely down to excessive heat and overloading, or also is actual distortion down to over zealous torquing.
I have a tendancy to under torque bolts, that is to say, do less than recomended, [where I think appropriate that is :oops: ]  
Head gaskets deteriate,and  fail after time too, but I'm wondering if extra care in attaching the head to the block increases the chance of reusing the head post gasket failure...

they say to torque the head down in a sequence for a reason, as well as removing the bolts/studs in the same sequence.  this is to reduce the likelyhood of 'warping' the head.  the distortion of the head/block is directly related to the torque applied to them.  this is why good engine rebuilders will use a torque plate to hone the cyl walls  :wink:  i would imagine that after heat failure, the head will require re-surfacing, or even be rendered non-repairable.  the fiber gaskets must be prone to failure over time, but i would assume the 1.9 head gaskets to be a big improvement, and since made from 100% metal, should not fail under normal circumstances.  but must be changed each time the head is removed, much like heat shields must be changed when pulling the injector.

now about the ARP studs vs Raceware - i believe that the raceware ones have much less of a thread pitch than ARP.  they require about 50-60 ft/lbs whereas ARP require 80 ft/lbs with their lube.  i would say that Raceware's 'unique' coating to be matched to ARP's moly lube.  i had a very nice sheet with my racewares that i lost, but it described torquing in good detail.  it talked about friction losses, etc.  and about clicker torque wrenches vs beam, and another type i forget... thread pitch has a lot do with it as well.  as you can imagine, it will be much easier to turn the nut that uses a very low thread pitch, and thus decreases the torque required to achieve the same clamping force.  you can relate this to gearing.. 1st gear in the car requires lots of engine rpm's to achieve the same speed as the car in 5th gear, but the power output to the wheels is greatly reduced in 5th gear.  

hope that helps!

[zukgod1]

and a retorque after one heat/cool cycle.

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

Chris

The ARP tech told me a retorque was not necessary on studs as they are not stretch fasteners.

A standard head bolt stretches thus the retorque needed but studs = no stretchy.

I'm not saying don't do it just repeating what i was told.

That being said when I get my G60 VC back from powder coating I'm going to add 1/8 or 1/4 turn to each stud while it's off.
Kinda scary though as I'm already @ 100 ft lbs.