I wanted to hear from those using ARP head studs who have tq'd them over the ARP suggested 60 lb ft.

There are ssssso many different suggestions from many different people here as to the final tq spec. Who came up with using more tq than suggested by ARP and why?

It's common-sense to use the tq specs BMW gives for anything else. Why not ARP?

possibly because ARP isn't giving torque specs
specifically for boosted applications?

Because you don't torque elastic range and plastic yield fasteners to the same torque value for the same clamping load and fastener strength/longevity/fatigue life etc.

60 ft-lb on the ARP studs is what matches the stock bolts in terms of clamping load. (about 10,000 lbs.) more torque will very quickly get you to (or beyond) the limit of the limits of the stud (12,500 lbs).

If anyone took the 5 mins to call ARP and ask what a 10mm undercut stud in the BMW kit is to be torqued to, they'd tell you ;)

:rolleyes
we should be ashamed.

techno:
what specs does trm use when dealing with arp head studs
jon:
would you be kind enough to divulge the torque specs arp suggests for us.
the title of the thread suggests 60:confused

If anyone took the 5 mins to call ARP and ask what a 10mm undercut stud in the BMW kit is to be torqued to, they'd tell you ;)
60 ft-lb.

techno:
what specs does trm use when dealing with arp head studs

we have tried a variety of different things with the studs. Most/all of them resulting in some sort of issue is what prompted us to work with ARP to find a solution. We have since had them test some BMW head bolts to verify the targets and are using that data to spec a better stud.

60 ft-lb on the current ARP studs matches the stock bolts torqued using bmw factory specs, and provides around 10,500 lb of clamping force.


The current ARP stud is an undercut 8740. as noted above, it provides 10,500 lb of load at 60 ft-lb. The stock bolts provide 10,000 lb of load. The yield strength of the ARP stud is around 12,500 lb. Yield strength of the factory bolt is 14,500 lb.

The new ARP solution will address the clamp load similarly and also greatly increase the tensile strength. It will still be 10mm and it will not be a straight shank stud.

As mike says - it is 60 ft lbs. If you guys ever have questions ARP (direct) are probably the most helpful people ever! I don't use 10mm studs, but I know they are 60 ft lbs, but never accept someones claim without substantiating it with the manufacturer - but, I know 60 ft lbs to be correct.

Don't mind me butting in, I was in the same situation as alot of you about a year ago when doing my headgasket (not that my car is done............dammit) but I followed CC's instructions and may have tightend to somewhere around 80 ftlbs?!?!? I figured if his car held as high as it did he must have done something right? Either way, take it for what it's worth , I'm not changing whatever it is right now so we'll see. I may be able to research back to the original post and see what I followed.

Every time I went much over 60ftlbs (around 70) with arp 10mm studs I noticed the nut never would thread on right, I believe it slightly streached the stud. I now run the 12mm studs and go to 75ft lbs.

yep over 60 ft lbs you definitely stretch the stud. No good.

an oversized stud isn't necessarily a good solution either. For a fastener to function properly it must be stretched a certain amount. The "spring in tension" effect is what provides the clamping force. The idea behind the undercut stud was the ability to get the fastener into its "stretched enough" range at a reasonable load. Too big and you will need too much initial force to get it to the stretch point (or you'll just never stretch it).

Even the new ARP solution won't be straight shank 10mm.

That's fine - they can re-design whichever they please. I am trying something else.

so techno when is this newly designed arp stud going to be for sale.

an oversized stud isn't necessarily a good solution either. For a fastener to function properly it must be stretched a certain amount. The "spring in tension" effect is what provides the clamping force. The idea behind the undercut stud was the ability to get the fastener into its "stretched enough" range at a reasonable load. Too big and you will need too much initial force to get it to the stretch point (or you'll just never stretch it).

Even the new ARP solution won't be straight shank 10mm.


Also- a given gasket is only capable of sealing up to so much. Some of the thicker MLS gaskets with more layers will actually seal more head lift. It may be worth trying to chat up an engineer at cometic and see what their tech guys have to say about how much head lift is acceptable with what gaskets. That would give you a place to start if you knew the youngs modulus of the steel used in the bolts to design something that would work for at *least* 3000psi cylinder pressure.

Pardon my bmw newb-ness but are the factory bolts stretch bolts or do they operate in the elastic region- and if they are in fact 14,500 lb total strength why not run those over the 10mm (existing) arp kit? We've had no problems whatsoever with the 10mm x 1.50 victor reinz stretch bolts used in vw 20v, even in engines producing over 700bhp on a superflow / 3000+ psi cylinder pressure, however we have had problems with the aftermarket stud kits for them, although this is mostly due to the application (those heads suck).

What applications are the larger stud kits being sourced from, the 11mm and somebody mentioned half inch kits? They aren't listed under BMW so that would lead me to believe from past experiance that these have been found from other applications.

Everyone should read......and understand this :
http://www.boltscience.com/pages/basics1.htm (http://www.boltscience.com/pages/testservices.htm)

Edit: fixed the link it lead to the wrong page.

Hmmm one could probably rig up the torque to failure / torque to yield test using a strong fixture and a load cell of some sort with a couple of strain gages. If we had data for the OEM bolt, and various other bolts it could prove to be quite insightful. I will try to think about a good cheap / easy to build test rig and see what I come up with.

Bolt it trough something, block of steel, I would not use an engine, draw or print 360°angles on the top of the piece, lube and torque the fastener in 5 lb/ft increments and note the angle of every step, at the yield point the angle will start increasing.
Anyone have a junk stud to destroy for science ??


Edit : woot...1000th post, sorry to have annoyed you this much :D

i believe I torqued to 80ft lbs. this is what worked for me regardless of it being right or wrong.

I torqued to 60 ft lbs because that's what ARP recommended. ;)

Bolt it trough something, block of steel, I would not use an engine, draw or print 360°angles on the top of the piece, lube and torque the fastener in 5 lb/ft increments and note the angle of every step, at the yield point the angle will start increasing.
Anyone have a junk stud to destroy for science ??


Edit : woot...1000th post, sorry to have annoyed you this much :D

You can get them for $10 a piece at Summit.

Yes, that would work to get us a rough version of the yield point. I was more thinking a calibrated strain gauge to read out actual force and then take a reading every 5 lb-ft until either it fails entirely or I can't turn it anymore LOL. That would give us a true torque / force reading- I suppose actual strain could easily be measured at the same time, and tensile stress could be calibrated. It would give us enough data to where we could say "the highest force this fastener can deliver is xxxxx so we need to stop at yyyyyy, to allow zzzz cylinder pressure and get the maximum clamping force without exceeding the yield point, or the ultimate tensile stress- if you want to replace them every time"

Like I said, give me a minute to think about the rig- Its easy to think of a rig that will work for the actual experiment but harder to think of one which is easy to calibrate or manually put a large force on- all without spending a fortune. BTW, how long are the bmw head bolts / studs underhead length?

yep over 60 ft lbs you definitely stretch the stud. No good.

Maybe I haven't looked hard enough but I've never seen this proven with our studs on a bmw motor. Have you or are you just guessing?

I have, go to 65 - 70 ft lbs and try and thread the nut all the way down the stud before you have the head on

You mean for instance your had studs in your motor, torqued them to 70ft lbs , pulled the head back off and then tried threading the nut all the way down the stud?

Not on my particular engine, but yes.

What Jon says here is 110% true. Over torque even to 65ft/lb and you will distort the threads and prevent the nuts from threading down.

Yep - it'll thread down but it will be pulling the threaded shaft back into place and or distorting the threads which ultimately blows any hope of having an accurate idea of how much torque is on the stud the 2nd time around

PITA to say the least. Does anyone have the length spec of a brand new stud?

Yep - it'll thread down but it will be pulling the threaded shaft back into place and or distorting the threads which ultimately blows any hope of having an accurate idea of how much torque is on the stud the 2nd time around

You've distorted the THREADs on a 10mm ARP undercut stud???? That would be a first....that I've seen anyway. You sure you didn't stretch the stud to the point where the 12pt nut ran into the shouldered part of the stud and messed it up? That's kinda what the undercut is there for....over-torquing results in the stud stretching via the undercut portion....eventually they will reach ultimate failure(undercut portion yields)long before any threads get messed up.

Don

Don yep it was jacked up. I didn't measure the studs before we did them on my friends motor, but yeah the nut was not smooth in going back down the shaft. This has been noticed by a few other guys on here as well. It sucks thats why I am not real convinced in the undercut that ARP designed.

Sigma you can't have a "what is the length" because every stud will be slightly different. You should have measured the studs before they went in - this is what goes in a "blue printed" motor :)

Shouldn't every stud be the same length? I'd think so, just like a M10x100 is going to be 100mm long...

What Jon says here is 110% true. Over torque even to 65ft/lb and you will distort the threads and prevent the nuts from threading down.
The threads won't distort at a reasonable torque. It is the stud that stretches.

You've distorted the THREADs on a 10mm ARP undercut stud???? That would be a first....that I've seen anyway. You sure you didn't stretch the stud to the point where the 12pt nut ran into the shouldered part of the stud and messed it up? That's kinda what the undercut is there for....over-torquing results in the stud stretching via the undercut portion....eventually they will reach ultimate failure(undercut portion yields)long before any threads get messed up.

Don
this man speaks the truth.
Don yep it was jacked up. I didn't measure the studs before we did them on my friends motor, but yeah the nut was not smooth in going back down the shaft. This has been noticed by a few other guys on here as well. It sucks thats why I am not real convinced in the undercut that ARP designed.
the undercut is how you get the bolt in its elastic range at reasonable forces.

Techno I fully understand what the undercut is for, however, myself and others have had the same instance - torquing slightly over 60 - 65 ft lb and the bolt stretches @ the threaded shaft, it might be stretching at the undercut as well, but when a nut takes effort to thread down without even clamping yet... do the math.

Just to clarify- the elastic zone of a material starts at 0 strain- so sitting there in the box, they are "in" the elastic zone. My guess is ARP looks to generate a certain amount of strain such that the studs do not unload during heat cycles and such. However, I don't see a disadvantage to using a larger stud and simply torquing them higher and generating more clamping force, unless the cylinder head / block don't have enough meat for that and distort excessively. I think what may be happening is people are raising the torques thinking it will give hem more clamping force- which is probably true- but the actual loading is the clamping force PLUS the cylinder pressure, so if they are right there at the ultimate tensile stress just from the torque, then you'll be on the downside slope towards failure when load is placed on them- and the strain will go up hence your head lifting.

On the motors that blow headgaskets, has anybody actually observed stretched studs? Measured before / measured afterwards? How many of these guys are reusing studs that were overtorqued to begin with?

Is it possible to buy the studs 1pc at a time, if so I would probably buy some to perform the torque / force testing.

Just to clarify- the elastic zone of a material starts at 0 strain- so sitting there in the box, they are "in" the elastic zone. My guess is ARP looks to generate a certain amount of strain such that the studs do not unload during heat cycles and such. However, I don't see a disadvantage to using a larger stud and simply torquing them higher and generating more clamping force, unless the cylinder head / block don't have enough meat for that and distort excessively. I think what may be happening is people are raising the torques thinking it will give hem more clamping force- which is probably true- but the actual loading is the clamping force PLUS the cylinder pressure, so if they are right there at the ultimate tensile stress just from the torque, then you'll be on the downside slope towards failure when load is placed on them- and the strain will go up hence your head lifting.

On the motors that blow headgaskets, has anybody actually observed stretched studs? Measured before / measured afterwards? How many of these guys are reusing studs that were overtorqued to begin with?

Is it possible to buy the studs 1pc at a time, if so I would probably buy some to perform the torque / force testing.

Yes, it starts at zero. I don't think anyone said differently. They just referenced the "zone" at X torque load. Meaning(like you are saying)the fastener needs to be in a state where the clamping forces are enough to keep the combustion event inside the cylinder BUT the fastener allows movement necessary to allow for expansion/contraction....AND, the important part, NOT allow that to alter it's clamping force. Or in short, not fatigue to failure.

The real question is what are the parameters?:D What are the values? I'll admit, I'm guessing in my build. I like the sound of what 1/2" studs will do but I don't like the fact that they are straight cut and will have very little elasticity. That's why, after discussion with ARP and Cometic I selected the 12mm x 1.5 undercuts. They will be torqued to 75ft/lbs and then retorqued after a couple of heat cycles to 80ft/lbs. I'm using a Cometic MLS gasket at .70thk with 13mm head stud holes.

Based on the design of the block, you "could" drill through the blind holes that are the head stud bosses. This would increase your "perch" and improve pull out strength. You'd just have to make sure you seal the threads obviously. But IMHO, I don't think at 80ft/lbs I'll be having any trouble with that. My only issue was getting a new MLS gasket with 13mm holes instead of 12mm and drilling/tapping the block.

The tapping is actually being a real PITA since I cannot find class "D4" taps to tighten up my thread tolerance. I have D6 @12mmx1.5 but they give me somewhat disapointing results. Of course I'm using a test block at the same thickness as the head stud boss to test. I have one more source for a possible D4 tap and if that falls through, I'm using the D6!!!

So, if this works. Great. But then that brings in problem#2. Once we have satisfactory clamping force/stretch properties is the head design enough to take this?

I have also measured my studs from end of the thread(where the "roll" creates a shoulder)to the top of the stud. In effect, from where it threads into the block to the top of the stud above the cylinder. I've recorded all 14 and if I have a failure I'll be able to see what moved and what didn't.

Don

I like the sound of your choice of stud Don - we torque plated my block with out CNC torque plate (which is for rent to the community now!) and honed the engine with that preparing for serious head clampage. I like the idea of drill thru the stud threads but looking at my block I wasn't sure that drilling all the way through was going to clear all critical passages. It appears it would, but I didn't want to take chances. We drilled about 1/4" deeper than stock for 1/2" studs which will be torque to 90 ft lbs first and if any issues, then the big torque wrench comes out :)

Also my machinist didn't notice much movement at all when the block was torqued on the plate - that's reasssuring!

I like the sound of your choice of stud Don - we torque plated my block with out CNC torque plate (which is for rent to the community now!) and honed the engine with that preparing for serious head clampage. I like the idea of drill thru the stud threads but looking at my block I wasn't sure that drilling all the way through was going to clear all critical passages. It appears it would, but I didn't want to take chances. We drilled about 1/4" deeper than stock for 1/2" studs which will be torque to 90 ft lbs first and if any issues, then the big torque wrench comes out :)

Also my machinist didn't notice much movement at all when the block was torqued on the plate - that's reasssuring!

Isn't that something with the bore movement? I measured mine with and without the head torqued down and was surprised at less than .0004 variance in any direction, top and bottom of bore. The concentricity was amazing! You'd never see that in a SBC!!

A 1/4" deeper than stock? Wow, that's cool to know. Thanks for passing that on...I feel safer once I start drilling!!

We investigated the cooling flow on the BMW engine last night. We can do direct cooling though the sides of the block at the core plugs and get rid of all that heat being directed in and around cylinders 5-6 and at the end of the head too. We considered reverse cooling too but we'll do this first and see what our temps are before getting crazy.

Do we need to do it? Dunno. Cooling seems to be a non-issue if you have a larger radiator, decent water pump and a oil cooler. But I figured since we have the block on a stand, it's sure easier to drill the ports now. I can always plug them later if things don't work out.

Don

Yea- just wanted to make sure- over in VW land- people are not too educated as to the elastic region, plastic region, yp, uts, etc. Appears you guys have a better handle on things :)

Would it be worth my time to measure some of the force data for the various studs experimentally- IE, would anybody be interested enough in seeing that data to make it worthwhile me building a fixture and setting up an op amp circuit / strain gauges / calibrating etc. to collect and compile the data. It may yield some interesting infomation as to the proper torques for certain studs and possibly what studs are appropriate for what applications.I suppose I could call the fastener testing place and just check what they want per sample also considering the effort of building a fixture and such it may make sense just to pay them to do it.

Yea- just wanted to make sure- over in VW land- people are not too educated as to the elastic region, plastic region, yp, uts, etc. Appears you guys have a better handle on things :)

Would it be worth my time to measure some of the force data for the various studs experimentally- IE, would anybody be interested enough in seeing that data to make it worthwhile me building a fixture and setting up an op amp circuit / strain gauges / calibrating etc. to collect and compile the data. It may yield some interesting infomation as to the proper torques for certain studs and possibly what studs are appropriate for what applications.I suppose I could call the fastener testing place and just check what they want per sample also considering the effort of building a fixture and such it may make sense just to pay them to do it.

Well, I don't know if I have a better handle on things than the VW guys:)...I used to hang out on www.passatworld.com (http://www.passatworld.com) for some time messing with my daughters 1.8T with a GIAC chip and some stuff...some pretty sharp guys in there as it sounds like you are.

I don't know how busy you are but I know I'd sure like to see the data. Do you know of anyone with a tinius-olsen or structron tester? I know if I was back in my old test lab I could do it in about 1 minute per fastener!! Have a nice plot of the yield in/lbf curve on paper too.

You can bet ARP has that data already...prolly Mike(techno)too:devillook

Don

The real question is what are the parameters?:D What are the values? I'll admit, I'm guessing in my build. I like the sound of what 1/2" studs will do but I don't like the fact that they are straight cut and will have very little elasticity. That's why, after discussion with ARP and Cometic I selected the 12mm x 1.5 undercuts. They will be torqued to 75ft/lbs and then retorqued after a couple of heat cycles to 80ft/lbs. I'm using a Cometic MLS gasket at .70thk with 13mm head stud holes.

Based on the design of the block, you "could" drill through the blind holes that are the head stud bosses. This would increase your "perch" and improve pull out strength. You'd just have to make sure you seal the threads obviously. But IMHO, I don't think at 80ft/lbs I'll be having any trouble with that. My only issue was getting a new MLS gasket with 13mm holes instead of 12mm and drilling/tapping the block.

So, if this works. Great. But then that brings in problem#2. Once we have satisfactory clamping force/stretch properties is the head design enough to take this?

I have also measured my studs from end of the thread(where the "roll" creates a shoulder)to the top of the stud. In effect, from where it threads into the block to the top of the stud above the cylinder. I've recorded all 14 and if I have a failure I'll be able to see what moved and what didn't.

Don

I like the sound of your choice of stud Don - we torque plated my block with out CNC torque plate (which is for rent to the community now!) and honed the engine with that preparing for serious head clampage. I like the idea of drill thru the stud threads but looking at my block I wasn't sure that drilling all the way through was going to clear all critical passages. It appears it would, but I didn't want to take chances. We drilled about 1/4" deeper than stock for 1/2" studs which will be torque to 90 ft lbs first and if any issues, then the big torque wrench comes out :)

Also my machinist didn't notice much movement at all when the block was torqued on the plate - that's reasssuring!

Isn't that something with the bore movement? I measured mine with and without the head torqued down and was surprised at less than .0004 variance in any direction, top and bottom of bore. The concentricity was amazing! You'd never see that in a SBC!!

A 1/4" deeper than stock? Wow, that's cool to know. Thanks for passing that on...I feel safer once I start drilling!!

We investigated the cooling flow on the BMW engine last night. We can do direct cooling though the sides of the block at the core plugs and get rid of all that heat being directed in and around cylinders 5-6 and at the end of the head too. We considered reverse cooling too but we'll do this first and see what our temps are before getting crazy.

Do we need to do it? Dunno. Cooling seems to be a non-issue if you have a larger radiator, decent water pump and a oil cooler. But I figured since we have the block on a stand, it's sure easier to drill the ports now. I can always plug them later if things don't work out.

Don

Jon and Don put all these things together and you will alsmost have the best solution for what we have.

remeber arp underates there bolts by about 20%.

Oh another thing I found chamfer your bolt holes even over drill hole a 1/16 in before starting tap.

Also you can drill and tap a little more than 1/4 inch deeper

The 1/2 studs I run can be tourqed up 125ft lbs I use 95.

100_0382 (600 x 338).jpg

Here you can see the stud holes - drilled larger for about the top 1/8 - 1/4" or so to take the load off the stud @ the deck.

http://blowneuroz.com/525/Machining/machining6.jpg


I too am using 1/2 that are about 125 or so

Here you can see the stud holes - drilled larger for about the top 1/8 - 1/4" or so to take the load off the stud @ the deck.

http://blowneuroz.com/525/Machining/machining6.jpg


I too am using 1/2 that are about 125 or so



exactly:buttrock

Thanks for the clarification CC!! I was really worried since my threads were coming up about .080 too long!! Looks like I'll have np drilling that extra depth.

Yes, I also planned on counter-boring the holes at the same ratio/depth as the factory. Mine goes up on the mill tomorrow night.

Thanks again

Don

I think what may be happening is people are raising the torques thinking it will give hem more clamping force- which is probably true- but the actual loading is the clamping force PLUS the cylinder pressure, so if they are right there at the ultimate tensile stress just from the torque, then you'll be on the downside slope towards failure
It fact, these forces don't add up, head lift force is subtracted from the clamping force, if it becomes greater than the clamping force the head will lift.
Imagine that they are the same, the cylinder pressure is pushing the head with an equal force as the studs pull, the head haven't moved yet, so the studs "see" the same force but the force between the head and block is=0.
When the head lifts, stud loading start to increase, otherwise it's linear.
Gasket failure should happen before the head lift since the combustion pressure push it out.
Read the link I posted in the other page at the end it gives really good infos on blot science.

I was talking about the force in the studs, not the clamping force between the head and block which yes as you said is decreased- the force in/on the studs is increased.

We were talking about studs and testing of studs and forces generated by studs, I guess I was not clear enough.

-Pete

5mall5nail5 or anyone else using it, can you tell me the part for the 1/2 arp studs. Because im in the middle of my build and i wanna nip this problem in the butt.

5mall5nail5 or anyone else using it, can you tell me the part for the 1/2 arp studs. Because im in the middle of my build and i wanna nip this problem in the butt.

call arp, they have several different setups

which is the one your using?

Its a proprietary New Sweden stud


No seriously call them and tell them what you want to do - I don't want to give my setup out because its specific for my use.

I was talking about the force in the studs, not the clamping force between the head and block which yes as you said is decreased- the force in/on the studs is increased.

We were talking about studs and testing of studs and forces generated by studs, I guess I was not clear enough.

-PeteI'm talking about the studs, the tension is constant from the day you torque them, it does not see the combustion pressure at all.
The point is that the clamping force and the lift from combustion don't add up on the stud tension.
Read the link here please, it seem the other one lead to the wrong page, fixed sry.
http://www.boltscience.com/pages/basics1.htm

Ha, yes, you are correct. Had to stop and think about that for a sec. :)