Broken DPS Headstud?

Well, one of my driver's cylinger headstuds broke off. These were ordered from DPS about 2 years ago. Not many mile have been put on them at all, tops 6,000. I drove it for a few months, then the truck went into "build mode" and is now a project, so thats the reason for such low miles.

Anyways, aren't these things supposed to be rated at 280,000 psi or something like that? It sheared right below the last (top) thread in on the end that threads into the block. Max boost I ever saw was 15 psi, and that was once. Every other time it had stayed around 9-12. So that wasn't the cause I don't think. Fuel was turned up about 1.25 flats with Stage 1's, not much black smoke, so thats not the cause. I can't figure this out.

The most curious thing about it is I found it on the ground next to the truck. I don't think its possible to just rattle its way out of the cylinder head after shearing off.

It will be easy to claim improper installation, but I did it by the book. I'll start calling Ken in a week when I actually can manage... I'm back off to school so time is hard to come by right now, I'm attempting to wrap up far too many things. I'll get a picture tonight. I'm pissed.

Wierd! Hard to believe that 6" worth of broken stud would jiggle off of the top of the head and onto the ground. Maybe you took an 8' jump that you don't remember?

Diesel Fly said:

Wierd! Hard to believe that 6" worth of broken stud would jiggle off of the top of the head and onto the ground. Maybe you took an 8' jump that you don't remember?

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Haha yeah, right as I was parking the truck. When I said I installed them "by the book" I really ment I installed them per Ken's over the phone instructions.

Sounds like a freak defect of some kind. Maybe a porosity issue in the steel. I doubt there is anything that anyone could have done to cause it. How about some close up pictures of the break?

I would bet that with the tension those studs are holding, when it failed it popped out of the hole. It really does suck. Can you use an easy out through the head hole? Smear some grease in the hole to catch the filings as you drill the hole? Probably a stretch...I'm just throwing ideas at you.

Paul

If I can find a 6" + easy out then yeah it will probably work. I'm sure as hell not ready to pull a cylinder head, as that means pulling the engine due to the studs. I'm in the middle of fixing the neighbor's gate right now (lunch), but when I finish that, pics will be here.

It's been a while since I had any need to call Ken but if things are like they used to be, You better start calling now to speak with him next week. IIRC, the best time to get him is 10:00am his time.

apextrans said:

It's been a while since I had any need to call Ken but if things are like they used to be, You better start calling now to speak with him next week. IIRC, the best time to get him is 10:00am his time.

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Yeah I know... I guess I should.

I stated two things wrong.

1) I wouldn't have to pull the engine to remove the remainder of the stud or to replace the new one, as the broken stud couldn't have come out if there were clearance issues.
2) The stud actually broke on the lower portion of the thread:



So perhaps it fractured, then continued to back its way out of the rest of the threads in the block?

That picture shows the stud was not threaded completely into the block. Ken asked me to help with the design of these studs so I told him what the length should be and to remove the 1 or 2 bottom threads. That way they could be turned all the way down till they bottomed out and not ruin the bottom thread. The way they are built is set up for a good reason. Most builders wil understand blinding a bolt in a blind hole. So these studs really can't be sent to the bottom of the block. What you do is install them with 1 or 2 threads showing above the nut. That way they work for all blind holes and you can't have one frozen in the block. A bolt or stud under torque will have plenty of tension on it when it fails thus the shooting out of the head condition you have here. The early studs were 270,000 psi and the later studs were 220,000 psi. Ken has posted that his supplier is having "problems" making them these days. I haven't talked with him about solving this yet.

I know you can't see the other end very well in the picture, but there are only a couple threads sticking out of the top. This could only really be explained by the stud being too short, which I highly doubt. In order for it to shoot out when a proper length stud was properly threaded in and seated at the right depth, the stud would have to rip the threads in the block out. One way that is possible is if the stud was over torqued during installation (highly unlikely, you install them with a Hex wrench) or due to over torque the stud nut on top of the cylinder.

Also, the rust on the threads suggests that the stud wasn't seated on that portion of the thread. Again, I can only explain this with the theory of a short stud, but that is unlikely since good R&D was probably done for these studs.

The "problems" with the supplier... Do you know any more about that?

isnt that a head bolt, not a stud. Wouldnt a head stud be threaded at both ends?

If you can I would have that stud tested for breaking strength at a lab that can handle it. If not send it to me and I'll have it tested. Then we all will know the breaking strength. Maybe even why it broke. Now the bigger question nobody seems to want to ask is what are the other 33 studs looking like? Sorry but it has to be addressed sooner or later.

Personally I'd pull the rest of that stud if I could get an easy out on it, and either buy or have just 1 more made and hope for the best with the others. Maybe not the best, but that's what I would do so long as the heads are not leaking at the moment.

icanfixall said:

If you can I would have that stud tested for breaking strength at a lab that can handle it. If not send it to me and I'll have it tested. Then we all will know the breaking strength. Maybe even why it broke. Now the bigger question nobody seems to want to ask is what are the other 33 studs looking like? Sorry but it has to be addressed sooner or later.

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Yeah, I know. I'm going to do what JD said, and after fixing the one, hope for the best & check them very often. As for the testing... I don't know anyone who does that type of testing... How much does that typically cost?

Diesel JD said:

Personally I'd pull the rest of that stud if I could get an easy out on it, and either buy or have just 1 more made and hope for the best with the others. Maybe not the best, but that's what I would do so long as the heads are not leaking at the moment.

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Yeah I'm not willing to pull the engine and replace them all at this point. I'd buy a Cummins and swap it in.

MUDKICKR said:

isnt that a head bolt, not a stud. Wouldnt a head stud be threaded at both ends?

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It is a stud, and it is threaded at both ends. the other end is out of focus & is a fine thread, so its hard to tell in the picture.