Head studs torque

[Zeus]

Hi all,

Does anybody know the actual torque the OEM head studs are torqued to? I am talking about the torque that is achieved after the 180 degree turn after the 60Nm.

How does that torque value compare to the torque used for the ARP head studs? Is it a lot lower?
I read that the ARP's should be torqued to 80 ft lbs (108,5Nm).

Alternatively, if someone can tell me the thread pitch, bolt stem diameter and length of the non-threaded part between the head and the thread I could also approximately calculate it. So that would help too.

[Rusty]

The original bolts are stretch bolts so the angle takes them over the yield strength. I believe that it's a way of making sure that the clamping force is more uniform, as it is determined by the yield strength of the bolt and not the torque applied.

[Zeus]

I'm aware that they are stretch bolts, but then you can still calculate the torque, assuming that they're still 10.9 grade or something similar.

Also, once they're stretching, the torque value won't increase anymore, so you can still measure a certain maximum torque, and compare what clamping force you get with that torque compared to the torque spec of the ARP bolt's.

It's just to understand how big the increase in clamping force is of the standard bolts VS the ARP's.

So if anybody knows some values or has a set lying around they can measure (both OEM and ARP's are welcome), that would be appreciated.

[UrS4boy]

AAN Cylinder Head Bolt info for those not switching to ARP studs when doing a headgas

Hi all, Does anybody know the actual torque the OEM head studs are torqued to? I am talking about the torque that is achieved after the 180 degree turn after the 60Nm.

I was going to correct you on the "stud" thing but I see further down you say that you know the OE "studs" are actually bolts.

With that in mind, here is some info:

AAN Cylinder Head Bolt info for those not switching to ARP studs when doing a headgasket:

http://forums.quattroworld.com/s4s6/msgs/245478.phtml

[Zeus]

Thanks, do you by any chance also know the size of the bolts (non-threaded cross section and length of the section)

I did make a little error in the post, but hey, the ARP's are studs so

I was referring to the fact that they are stretched in my second post, but didn't notice the stud error.

[UrS4boy]

Thanks, do you by any chance also know the size of the bolts (non-threaded cross section and length of the section)

No but if you hum a few bars, I can fake it.

PN = 034103385C

https://www.ecstuning.com/b-genuine-...ch/034103385c/

[Zeus]

So I ordered a box of the Victor Reinz bolts.

These are 12.9 grade bolts, so the tensile strength is at least 1200N/mm2.
To quote it in the numbers ARP presents on its website, that would be at least 174000 PSI.

I also measured the bolts at 107mm from the head (but not including the head) to the beginning of the thread.
Nominal cross section is 10mm for the non threaded and non ribbed sections on the Reinz bolts.
The ribs on the ribbed center section reduce the thickness by about 0,7mm (so 1,4mm on the diameter). The ribs consist of 3 spirals. I'm not sure about their effect, but I think they serve to stiffen the bolts in the rotation direction during tightening, and that they don't really contribute to the clamping load.

That gives us an effective diameter of 8,6mm for the Reinz bolts. Preload (neglecting the torsional load) would then equal about 63000N for each bolt at the point where it starts to yield (1080N/mm2).

If anyone has the dimensions for the ARP bolts to add to this, that would be nice. Then we can compare .