How many guys have used the ARP Studs?

[zigg]

As some of you may know I'm having trouble with my new rebuild. I put the thing together with ARP Studs, and so far it looks like the drivers' side head has cracks in 3 cylinders, or 1 that runs the length of the head, and somehow misses #6. I'm going to test the passenger side today.

Click here for the thread(long)...

I've talked to the guys(DAS) who did the machine work on both the block, and built(and supposedly tested) the heads, and Paul, although he's willing to look at the heads when I get them off(we haven't talked about replacement yet) suggests maybe that there is a problem using the Studs on these engines instead of the bolts.

He recalls one other guy who had a cracked head right at startup, and he supposedly used studs as well. They sent him a replacement head, and never heard from him again.

I'm sure there are guys who have had heads with cracks that didn't use studs too, but I'm curious to find out how many have studs, with no problems at all...

Zigg

 

[sle2115]

Zigg,

We installed many sets of ARP studs at the machine shop. While I can count the number of 6.9 motors we worked on one one hand, they got studs if we put them back together. That being said, one thing that always concerned me about studs - bottoming them out, then applying torque. Basically, if that stud tightens after being installed, it is applying pressure to the bottom of the bolt hole. In many engines, this isn't a problem as the holes are opened to the water jacket. In a hole such as a 6.9 though, I was always concerned that torquing the bolt could in fact damage the block - but really don't see how it could hurt the head. Pressure applied is pressure applied rather by stud or by head bolt. I never really bought into the theory that studs clamp any harder than bolts though unless you tighten them more. Personally, if I were you, I would take the head(s) somewhere independant and get them pressure checked. Magnafluxing will show cracks, but pressurizing the casting will show leaks - not all cracks leak. I would then get in writing from said machine shop that the heads leak (if they do in fact leak) to cya!

Good luck and sorry to hear of the troubles.

 

[zigg]

That being said, one thing that always concerned me about studs - bottoming them out, then applying torque. Basically, if that stud tightens after being installed, it is applying pressure to the bottom of the bolt hole. In many engines, this isn't a problem as the holes are opened to the water jacket. In a hole such as a 6.9 though, I was always concerned that torquing the bolt could in fact damage the block - but really don't see how it could hurt the head.

I hear what you're sayin', but the threads on the bottom of the stud are actually shorter than the bolt threads, and the bolts never are expected to hit bottom, so when the studs are threaded in till they "bottom out", they are actually just running out of thread, not actually hitting the bottom of the hole. They actually aren't supposed to turn any farther, just the nut on the top threads then turns to apply the torque...

Have a look at the 2 side by side in the photo

..click here..

Zigg

 

[icanfixall]

A stud works by the incline plane principle just like any screw thread but it doesn't create the twisting problem that a bolt has. The stud uses the threads that the nut is tightened on and not twisting the full length of the bolt. If bolts worked as well as studs they would be in many heavy applications. When we repaired large steam turbines sometimes the high pressue case studs were 6 inch diameter and about 5 ft. long. We had to use bolt heaters to stretch the studs just so we could remove the nuts. When we assembled these large studs we heated them up and used a 4 inch impact wrench held up by a craine. We called it the Widow Maker. It took 6 men (not boys) to operate. Everybody pulled their own weight or somebody was going to get hurt..... Studs are far better at clamping down something.

 

[Agnem]

Locomotive power assemblies are held in using studs, and they get torqued to 350 foot pounds! I'd be surprised Zigg, if the studs killed those heads. However, that said, we all know studs clamp better than bolts, and if for some reason they were warped, even if they were never resurfaced, I can see where the same head that was on a bolted engine, might crack on a studded one.

 

[sle2115]

I hear what you're sayin', but the threads on the bottom of the stud are actually shorter than the bolt threads, and the bolts never are expected to hit bottom, so when the studs are threaded in till they "bottom out", they are actually just running out of thread, not actually hitting the bottom of the hole. They actually aren't supposed to turn any farther, just the nut on the top threads then turns to apply the torque...

Have a look at the 2 side by side in the photo

..click here..

Zigg

But, and this is a big but, if the stud should was small enough to fit into the hole (which in the picture it looks like it isn't) then you see where my concern comes from.

Well and like I said, I have limited assembly experience on 6.9's. I was the assembly guy for everything, but we just didn't get many in the shop for total overhaul. We did use ARP studs on everything we could though. I probably assembled 100 Small Block Chevies using them, of course the combustion chamber pressures were not this high, although some were probably close to an na 6.9 when they were blown/turboed!

I really feel for you and keep trying to think of what could be going on. Been inside many a motor and just can't seem to imagine air transferring like this unless there was an issue with the clamping force. Don't suppose ARP sent you studs a little too long do you!

Good luck, I will keep thinking about it.

 

[The Warden]

I hear what you're sayin', but the threads on the bottom of the stud are actually shorter than the bolt threads, and the bolts never are expected to hit bottom, so when the studs are threaded in till they "bottom out", they are actually just running out of thread, not actually hitting the bottom of the hole. They actually aren't supposed to turn any farther, just the nut on the top threads then turns to apply the torque...

Based on the bit of experimenting I did prior to installing the studs on my 6.9l, I'm not so sure about the bolt going deeper in. I'm 99% certain that the studs are running out of thread as opposed to hitting the bottom of the hole. However, based on what I found, even with the shorter thread length, the studs go deeper into the block than the bolts do. The bolts have quite a bit of unnecessary threads, and start clamping the heads down long before getting anywhere near running out of thread.

I took this picture after running the stud and the bolt down into one hole until it bottomed out, using tape to mark the point where they started coming out of the head, then putting them into a head and seeing how much they protruded out the bottom. There was 5/16" between where the bolt came out of the bottom of the head and the point at which the bolt would bottom out in the block hole. So, even with the bolt being capable of going into the block 3/16" more than the stud, with them going through the head first, the stud goes into the block 1/8" more than the bolt.

You must be registered for see images attach

I also noticed that there are a number of typos on my page where I wrote up this comparison in the first place so, if you were using that at all, I can understand why you may have been confused with what I had written...

FWIW, I haven't had a single problem with my setup. I torqued the studs down to 90 ft-lbs. I really can't imagine the studs being your problem...

 

[Diezel_Cowboy]

This goes with what a few others have said, but if a guy were to torque a stud to the same specification as a bolt then the stud would be much tighter than the bolt at the same torque spec. This would be due to the length of the bolt acting like a torsion spring on a small scale. It would not be different with a stud since only the nut itself is turning.
Turning the long bolt is like using a torque wrench in combination with a long extension, this will yield different results since the extension will twist. Also from the picture the threads on the top of the stud are fine thread? That will make a difference too. So the question is did you tighten the studs to the same spec as the bolts?

 

[69oiler]

i have studs. so far so good after 15000 miles

 

[typ4]

Those fine threads on the top end of the stud are what makes it clamp harder also. More leverage against the contact area and so on, I read about threads years ago and dont remember where but fine = more holding force.

 

[jauguston]

When I put the Hypermax turbo on my 6.9 I asked their Tech if I needed to do something with my head gaskets or head bolts with the addition of the turbo. He said studs were not a good idea and the stock head gaskets were fine. He said the '83-'85 head gaskets were a little weak but from '86 on they were fine. He said all that I should do was check the torque on the bolts and be sure they were at 85 pounds. He did not go on to say why studs were a bad idea so I took him at his word.

I have put abot 7000 miles on the engine since the turbo went on with no issues at all and my engine has to work pretty hard. It is in a motorhome that is a barn to push down the road and weights 15,000 pounds with the Samurai dragging along behind. I see 14 psi boost on long hills and 1150-1200 on the EGT.

I guess my question would be, why studs?

Jim

 

[sle2115]

jauguston,

I can remember at least three cases from here and the other place where turbos were added, head gaskets failed. While I can't remember the years of the engines, the headgaskets are known to fail, maybe they were all pre 86 engines. Bolts are as much if not more than the studs, studs have higher PSI break points etc. Now in your case, I would prolly do the same thing, if all was well, why not leave it alone and see how it holds up, apparently yours are working fine, but if you are rebuilding a motor, why not make whatever improvements you can, especially when you are going to replace the bolts anyway. The size of the bolts is what worries me, 7/16 inch, and that alone would be reason to use the strongest thing you can. And, I am guessing that you got one guys opinion, I have talked to several guys as well, and they all say use ARP studs. Who knows why each feels the way they do, but for every person who says not to use them, I am sure there is one that says to use them. Proof being in the pudding, higher break point is enough reason for me, especially on such a small bolt/stud!

I hope yours runs for years and as a previous owner of a 72 Winnebago (the original concrete block) I know what it takes to move an RV!

 

[Diesel JD]

Whoever says that its only the pre '86 6.9s that blows gaskets needs some reeducation. My 86 lifted both head gaskets shortly after I bought it and its not even turbocharged(yet) I think the consensus is that the head gasket problem has to do with a combination of teh small 7/16" bolts, the CDR valve, and the gaskets themselves along with block design. I would have used studs if I could have afforded them or knew you could without pulling the engine. Too many people have used them and had good results to assume they are a problem.

 

[jauguston]

2115,

The "one guy" was the Tech at Hypermax that has done hundreds of turbo installations on 6.9-7.3 IDI's. I would consider his information much more credible than the typical self appointed internet expert you see that has a opinion on everything. Not to say the guys you got that information from were wrong but there is a lot of difference in the experience level of the information providers we are treated to. Regarding head bolts, he said used head bolts did not need to be replaced with new ones. They do not wear out.

JD,

No one said that only '83-'85 engines "Could" have headgasket problems. The '83-85 engines had a different design gasket that was prone to problems so it was changed for the '86 model year. That gasket is not noted for having a problem. "Any" engine can have problems but that does not necessarily mean that all engines like it will have the same problem.

Jim

Jim

 

[zigg]

Warden

Thanks for that info, and

Based on the bit of experimenting I did prior to installing the studs on my 6.9l, I'm not so sure about the bolt going deeper in. I'm 99% certain that the studs are running out of thread as opposed to hitting the bottom of the hole. However, based on what I found, even with the shorter thread length, the studs go deeper into the block than the bolts do. The bolts have quite a bit of unnecessary threads, and start clamping the heads down long before getting anywhere near running out of thread.

You're absolutely correct. I pulled 3 separate studs this morning, one at a time, and did measurements. I measured the depth of the holes, the length of thread etc to compare the 2. What I found, is that the bolts don't bottom out in the holes. If they have a washer on(I can't remember if they do), then they're about 1/2" short of the bottom of the holes. If not a washer, then yest, 5/16ths, and turns out, the studs run out of thread before they hit bottom too, but they also have about 1/4" left.

I can't imagine in any way that the studs could be responsible for these symptoms. The only thing I can think of, is that if somehow both of the torque wrenches I've got (one is a snap on, one is a proto-professional)were out by a lot, then I might not have got the torque right. I just can't make sense of that, but I guess I'll have to see about getting one of them calibrated to be sure.

Since the clamping force of the studs is much more than the bolts, could it be that studs torqued to 85 is so much more force on the heads that it could crack the heads? I just can't see it. And you did yours up to 90?!!

I'm thinking more like my torque wrenches are way soft, so that I'm setting them to 85, but they're only clamping to 50 or so. That still doesn't make much sense, because you'd think the studs to 50 would probably still hold the heads down better than the bolts at 80.

Heck, I dunno, now I'm just rambling....

Zigg