ARP head studs

Squeeto · **Posted:** Fri Mar 23, 2012 12:27 pm

racertracer wrote:

VM will not ... disclose the name of the manufacturer.

This is typically the response that I expected.

Can you post the original information that VM disclosed from before:

racertracer wrote:

OK, I was able to get the info from VM Motori and I forwarded it to ARP ...

LMWatBullRun · **Posted:** Fri Mar 30, 2012 3:46 pm

ARP recommends that 12 MM 220ksi breaking strength studs be torqued to 125 ft-pounds when using ARP lube.

See link here- http://arp-bolts.com/pages/technical_torque_us.shtml

This yields a preload of 19,425 pounds of clamping force per stud.

Does anyone know the yield strength of the stock TTY head bolts? My D24 used 90 ksi steel IIRC; I would think VM motori would have used higher strength steels.

LMWatBullRun · **Posted:** Wed Apr 11, 2012 7:43 am

The FSM shows only an initial torque, and then several turn-of-bolt angle turns. This is slightly better than torquing the bolts, but still yield inconsistent results due to variation in thread finish and friction. Does anyone have a used head bolt or three to donate to science? I can have the yield strength tested to determine what the clamping force is, if I have the bolts.

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

200ft lbs seems like a lot to me. Stock CR Cummins is 90 and ARP recommends 122 with their studs, some builders recommend a little higher. For what it's worth, most of the daily driven studded Dodges are replaced one at a time. That's what I did with mine with 6 re-torques.

LMWatBullRun · **Posted:** Thu Apr 12, 2012 8:50 pm

yes, the one at a time method is what most VW TDI owners have done, as well as many Volvo D24 dieselheads.

I don't know where the 200 ft pound number came from; I was not able to see that in the FSM. All I could find was the turn of bolt method.

NotPicky · **Posted:** Sun Apr 29, 2012 12:30 am

Trying to make sense of this thread. So are there studs available from ARP for our 2.8L? I'm getting ready for big boost numbers and want to make sure that head gasket stays put.

LMWatBullRun · **Posted:** Mon Apr 30, 2012 10:05 am

NotPicky wrote:

Trying to make sense of this thread. So are there studs available from ARP for our 2.8L? I'm getting ready for big boost numbers and want to make sure that head gasket stays put.

So it would appear. They do not have a kit yet, and Jeep/VM Motori does not sell HG separately. What would be ideal would be a stainless steel HG for this motor. the other issue is the retorqueing. Removal of the cams is required to access the bolt heads/studs.

My thought originally was that the ARP studs would improve the clamping force on the HG, and reduce/eliminate the potential for leaks/HG failure/head warping if/when the motor overheated. These studs have virtually eliminated such problems in the VW CI/AL diesel D16/D20/D24 series motors, and my hope continues to be that they would do the same on the VM Motori 2.8, which is also a CI block AL head engine. However, nobody has done it yet, me included. Right now I am waiting for a long tap and a long weekend to arrive to try this out.

It looks to me as though starting with an existing already compressed and installed HG is the better option, as this would seem to reduce if not eliminate the need to retorque the studs.

NotPicky · **Posted:** Tue May 01, 2012 1:14 am

LMWatBullRun wrote:

It looks to me as though starting with an existing already compressed and installed HG is the better option, as this would seem to reduce if not eliminate the need to retorque the studs.

That was my thought as well, do it with the original HG. I knew they didn't have a kit. How do you go about ordering each individual stud and nut from ARP? Are all the stock head bolts the same?

racertracer · **Posted:** Tue May 01, 2012 6:45 am

I'll need some time to dig up the info I received, then have it scanned and post it here.

The accident set me back a bit.

NotPicky · **Posted:** Sat May 05, 2012 10:52 pm

racertracer wrote:

I'll need some time to dig up the info I received, then have it scanned and post it here.

The accident set me back a bit.

any luck?

racertracer · **Posted:** Sun May 06, 2012 7:05 am

This is the information I received regarding the head bolts, if you give the ARP factory representative this info, he/she will be able to advise you on which stock or custom head studs will work with our 2.8 litre VM CRD engine. They will need all the tech info regarding the engine (HP/torque) etc. http://arp-bolts.com.

Please share any of the info you receive from ARP regarding the head bolts, installation procedure, torq requirements etc.

NotPicky · **Posted:** Sun May 06, 2012 10:50 pm

Thanks, I will start pursuing them. Will post what I find out

LMWatBullRun · **Posted:** Fri May 18, 2012 9:16 pm

OooohKay!

With the information on the drawing above we can easily calculate the clamping force of the TTY head bolt and then see how the ARP stud compares. Thanks for posting that, RT, that was the information I needed.

The stock bolt has a minimum diameter of 10.75 mm; that means that the area of the bolt is ~0.141 in2.

The yield strength of the 37CR4 steel specified is given at 1060N/mm2 or about 154 KSI yield; breaking strength is about 175 to 200ksi. The elongation spec is to ensure that there is some margin between the final torque and the breaking strength.

doing the math, at yield the stock bolt provides about 22 ksi (21,700 psi) of clamping force. In theory. In reality, this clamping force is somewhat variable due to thread friction, manufacturing variation on the bolts, washer smoothness and head smoothness, HG density, strength, and susceptibility to creep, etc. My strong suspicion is that the folks who are having the coolant leaks and HG failures are the victim of stochastic variations on clamping force which lead to HG failures.

if we torque the ARP studs to 125 ft pounds, they provide about 19,400 pounds of clamping force at ~ 75% of yield. If we torque to 100% of yield, or 165 ft pounds, we have 25,900 pounds of clamping force; plenty of ability to meet stock specs. Doing the math, and assuming that we need to match the VM design clamping force, then we torque to 85% of yield, or ~140 foot-pounds. ( I probably will torque to 145)

Doing this one by one in the prescribed pattern, what I will probably do is do an initial torque for each fastener to about 100 FP in three steps, 50, 75 and 100. Once I have the whole set of 18 installed, then I will torque to 120 in sequence, and finally torque to 145 FP, using ARP lube.

Them's my thoughts. I will do this later this year when I do the timing belt.

racertracer · **Posted:** Fri May 18, 2012 9:36 pm

LMWatBullRun wrote:

stochastic variations on clamping force

Ok ... What is it?

LMWatBullRun · **Posted:** Fri May 18, 2012 10:03 pm

stochastic: Situations or models containing a random element, hence unpredictable and without a stable pattern or order; probabilistic variability.

Most engineering involves some variability in the actual performance of the components involved; the larger the sample the greater the extreme spread of the data, but the more sure you can be that you have a good idea of the ultimate extreme spread. My somewhat educated guess is that either VM Motori's sample size for bolt clamping force was too small, or they underestimated the actual variability of production motors WRT head bolt clamping force as opposed to the tests that they did.

If you go to the ARP site they have an interesting graph of actual clamping force versus torque which is worth a look, and illustrates the point I'm trying to make.

racertracer · **Posted:** Sat May 19, 2012 8:07 am

NotPicky wrote:

Thanks, I will start pursuing them. Will post what I find out

Not Picky: Did you speak to ARP, what was their response?

LMWatBullRun: The ARP tech said 100 ft-lbs torque for the stock studs, you are planning on going past that to 145 ft-lbs, will the stock studs hold up? Will you be speaking to ARP regarding this?

Here is the response that I originally received from the ARP tech: "The part number of the closest stud that we have on hand is AU5.400-2LUB. The nut is AUN12-1 and the washer is AUW875N. Acceptable torque with ARP Ultra Torque would be about 100 ft-lbs.

RT

LMWatBullRun · **Posted:** Tue May 22, 2012 8:55 am

racertracer wrote:

LMWatBullRun: The ARP tech said 100 ft-lbs torque for the stock studs, you are planning on going past that to 145 ft-lbs, will the stock studs hold up? Will you be speaking to ARP regarding this?

Here is the response that I originally received from the ARP tech: "The part number of the closest stud that we have on hand is AU5.400-2LUB. The nut is AUN12-1 and the washer is AUW875N. Acceptable torque with ARP Ultra Torque would be about 100 ft-lbs.

RT

The arp manual states that torqueing to 125 fp or 75% of yield is the generic spec, but that can vary depending on application. I have not confirmed my calculations with Arp yet but will publish the results when I do. Frankly, justin did not impress me, so I am going to talk to one of their real engineers.

It is also worth noting that there are kits available that can save money over the piece price. Per piece these studs, nuts and washers cost about $20 each.

racertracer · **Posted:** Tue Jun 05, 2012 6:37 pm

LMWatBullRun wrote:

Per piece these studs, nuts and washers cost about $20 each.

LTW, I would like to know more about the kit number and where you can procure the head gasket?

LMWatBullRun · **Posted:** Fri Jul 13, 2012 1:58 pm

racertracer wrote:

LMWatBullRun wrote:

Per piece these studs, nuts and washers cost about $20 each.

LTW, I would like to know more about the kit number and where you can procure the head gasket?

ARP sells kits which include these studs,

IIRC, several of the 4 cylinder TDIs use exactly this 12 mm stud; these kits have 10 studs, nuts and washers, and two kits might be cheaper than 18 separate studs etc. Don't have my arp catalog handy, but will look when I get a spare minute, hopefully some time before labor day.

I saw a SS HG listed in the Elring catalog, and was trying to get IDParts to stock it, so far no joy.

geordi · **Posted:** Sat Aug 18, 2012 1:51 pm

Part numbers, please!

What is the part number for the Elring gasket? I'll buy it direct from them if I have to, but I will be pulling the head entirely, so I need that.

Stud kit part numbers? I don't mind buying either a kit for another engine OR the individual studs / washers / nuts... But I need to know which ones will fit, and that they can take the 145ft-lbs that you determined would be the answer.

Thanks!

ARP head studs

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