ARP head stud info

[kjewer1]

This is copied from RKO, so I dont have to keep redirecting poeple to that site. All the good stuff from that thread will be here. Original is at http://www.racingknowledge.org/topic...=arp,stud,info


I blew a head gasket on my 12.1 run last week. In researching why it may have gone out considering I had only 23-24 psi, 20-21 degrees of timing, and zero knock, I came to this conclusion. Others have seen this as well. When putting this head on, I didnt have any of the ARP moly lube that you lube the threads with. According to ARP on dry new threads up to 95% of torque being applied is spent just overcoming the friction between the male and female threads. Since we cant use a stretch guage to set clamping pressure on the head gasket, we have to rely on ARP to do this testing for us and give us a corresponding torque value to set the studs to. Since the amout of friction and torque wasted in the threads varies significantly witht he lubricant used, you must use ARPs brand moly lube. They suggest toruing to 80 ft/lbs (I dont have the chart in front of me, but thats close. Check the chart on ARPs website) on thier moly lube. In the case that you dont have any, use motor oil, and it has to be 10w30 (again, f=the type of lube will affect the amount of friction in the threads), and torque to 110 or so. Thats a BIG difference. I have seen a few people besides me recently use oil and lose the head gasket. I found that you can get the ARP lube from summit. They dont advertise it, and a search on thier website didnt turn up anything. I went through ARPs catalog and found thier part numbers for it, plugged those into summits manufactures search, and found the stuff. Its about 7 bucks for a tube of it. Or 18 bucks for a can. It should be here tomorrow.

Also, ARP stresses that the studs have to be in the block hand tight. In my case some of them wouldnt go in by hand and I had to double nut the stud and drive it in. I took great care not to tighten the stud in the block. But still some of the nuts came loose, two adjacent ones in front of cylinder 1. I'm willing to bet thats where the gasket failure was. So I ordered the M12x1.25 chaseing tap from Mcmaster since the tap and die set I use doesnt have that size. Hopefully after chasing the threads with that tap the studs will go in loosely as they are supposed to.

Just for the info in case anyone is going to be using the ARP studs.

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My moly lube showed up today. The 6 dollar tube is pretty good sized I must say. Unfortunately, it came in the same box as Chads gay ass 5" tach, so I'm afraid to use it.

More interesting info from the tube.

Torque is a variable (referring to the amount of tesile pressure it puts on the fastener) dependant on the amount of friction for the lubricant used. Motor oil as a lubricant will run away from heat and pressure, causeing more friction and insufficient clamping loads that vary many hundred of pounds per square inch. ARP moly provides the most consistent clamping loads without having to measure the exact elongation of every bolt (stretch technique). Able to withstand pressures to 500,000 psi, effective from 30-750f.

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You must own a 7 bolt motor. The manual is correct, but thats for the stock "torque to yeild" or "stretchy" bolts. They use bolts that will strech and put the proper clamping force on the head regardless of the torque value you use, as long as you go past some point. But unfortunately just when you start to make some real power, they stretch a little more Plus they are not reusuable. Even if they are still within spec, I wouldnt use them.

If you go to www.arp-bolts.com you'll find a table that shows what torque to use. I believe its 86 for moly, 109 for oil. But I thought the little instruction sheet that cam with mine said 90 and 120. Either way, we use the 12mm studs for 6 bolts, 190,000 psi. 11mm for 7 bolts.

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They all went in beautifully by hand. I highly recomend anyone doing anything with the head off spend the 10 bucks and get the tap! Torquing to 80 pounds with ARP moly lube (summit) was so much nicer than the abortion that is torquing to 110 with oil... I'll never go back Its holding great so far, I've been up to 25 psi and 46 pounds per minute. In contrast when it was leaking on the 16g I was only at 38-40 pounds. We'll see how it does when I raise the boost this week.


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But to answer the question... The whole purpose of stretchy bolts is to take the emphasis off torqueing properly or measuring stretch to determine clamping force. You can look it at it like drastically lowering the resolution of the changes you make. So if you are off a little while using a normal torque method, it has a large effect. But with stretchy bolts, a large difference is a small effect by comparsison. In fact, once you start to stretch the bolt the torque will level off and then lower until it fails from fatigue. I'm no mechanical engineer, but this is how I understand it.

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Something else to add that I didnt see in that thread. The way you torque the bolts is very important as well. Be sure to follow the patter in the manual. Its basically just a pattern moving outwards from the center 2 studs. Dont go straight to the 85 or whatever ftlbs you are going to torque it to. Do it in a few stages. You want the last stage to be the biggest jump in torque. For example, lets say the last stage brought to 75 pounds. Chances are that when you set your torque wrench to 85 pounds, you wont even be able to move the nut, it will just click. Its like you ebrake. There isnt enough friction to slow the car down very well when it is moving, but when the car is stopped it holds it very well. It takes a good bit of force to get that nut moving again against all the driction in the washer/threads. I suggest 20, 40, 85. Do it smooth and dont stop moving the wrench until it clicks! Make you have enough range motion to swing it far enough around. Dont stop. If you do, back it off a little and do it again.

So the moral of the story is to chase the threads with the right tap (m12x1.25 for 6 bolt block, m11x1.25 for 7 bolt), clean and dry the hole after tapping, use only ARP brand moly lube (most stud kits come with a small pouch, but not all of them!), and use proper torque wrench techniques. Obviously be sure the block and head are clean and within flatness specs.


Lets add this to the sticky, shall we?

[EclipseRST]

Damn... Thanks Kevin! Consider it done~

[GotGrip666]

ok i know im slow at this but what is tapping? and should i have to do it?

[1g90gsx]

good write up kevin,i allways make sure there is no shit on the threads and in the holes so the head bolts torque right.like say a friend that hands you a head bolt that was dropped in the kitty litter and did not spray off befor he hands it to you.running a tap, i will do the next time i do a head gasket.

[TsiTalon9587]

Very nice and useful information Kevin.

I have read this before a while ago, I think you went over this at speedoptions? Anyway, when I was building up my 6 bolt I kept this info in mind. So far in pushing 39 lbs/min, I have not come across any problems.

As far as *continuing* to turn the wrench, I am a strong believer of. The analogy is perfect, and there are millions out there should anyone not understand that concept. I luckily noticed this when I was doing it, and it looks like it may have made all of the difference.

GotGrip666:
"Ok I know I'm slow at this but what is tapping? And should I have to do it?"

Tapping is using a tool, obviously called a tap, that looks like a bolt, but with half of it missing lengthwise. If you were to look at it from the bottom, it looks like a positive sign " + " . Each end of the "lines" making the sign has threads on it(going into this page). A tap is made of a very strong material, so when you Thread it in to the existing hole, it is capable to cutting off material that isn't supposed to be there. This is the same material that could potentially alter a torque reading should it get caught in the threads of the stud. Also it is why Kevin had a hard time hand tightening the stud in. So in essence, Yes you should do it. Hope that helped.

[kjewer1]

Yeah, I initially wrote this up for RKO I believe, but I usually cross post info like this on all the boards I'm on. It was before I was on here though.

To sum up what I said above, we can't measure bolt stretch or clamping force, so we have to use torque applied. Anything that changes that will change the clamping pressure. Since fasteners like ARPs are usually supposed to be used at about 90 percent of thier tensile strength, being off 10% in either direction can be bad, for obvious reasons.

An example is a chunk of dirt or rust in the threads, you torque it to the 90 ft-lbs, then after a few hot-cold cycles (expansion/contraction) that piece of rust is pulverized into a powder. Now the stud is loose Plus it would have created friction in the threads, which was gone over above.

So yeah, its very important to be sure those threads are clean. I lost a couple HGs right in a row at relatively low power (16g, 35-40 lbs/min), then went to running as much as 64 lbs/min without losing a single gasket in a couple years. The combination of ARP moly lube and proper preperation for the studs is all that I changed

[GotGrip666]

see what i dont get is how do you tighten the studs if the head slides right over them, like how does it secure the head?

[GotGrip666]

hey Kevin where are you from?

[TsiTalon9587]

The stud we are referring to is a double sided (threaded) bolt. Therefore, when you hand tighten them into the block, it is as if there is a bolt sticking straight up out of the bolt thread sitide up. With that, the head slides on top of these as you said, and then lube, a washer and a nut bolt it down.

These nuts (no pun intended) are what Kevin is referring to with regard to the importance of the torque setting.

If you just made a new post and no one has replied yet, please just edit your first post with the additional info/question.

Kevin is from the New England area.

[GotGrip666]

So Would I Even Have To Take The Studs Out To Do A Head Gasket Change?

[GotGrip666]

When you said before in the other thread that you didnt take out the exhaust mani and turbo Kevin, did you just mean that you just unbolted it and just pulled the head off?

[kjewer1]

You can leave the studs in, but I would pull them out and tap the holes again unless you are positive it was done last time.

I remove the 4 manifold to turbo bolts. The manifold with coe up with the head, and the turbo will stay there attached by the downpipe and the oil/water lines. Saves a whole shitload of work and time. Just cover the turbo inlet so nothing falls in there.

As Aaron said I am from the NE area, I do travel within reason to help poeple out. Just keep in mind that diesel isnt cheap these days

[GotGrip666]

cool is new york to far for you?

[Black99GST]

so you put the Head studs into the block only hand tight? the only torque to worry about is the torque on the nuts that go on after the head right?

[Blackcrow64]

Originally Posted by Black99GST

so you put the Head studs into the block only hand tight? the only torque to worry about is the torque on the nuts that go on after the head right?

Correct, and you posted in the wrong thread. lol