Changing from ARP 2000's to 625's---how to?

Joesixpack said:
If the stud can bottom in the hole, you can get a screw jack effect.

The friction between the nut and stud can put a fair bit of torque on the stud, so not only your holding the clamp load, but now have this "screw jack load" from friction wanting to turn the stud in more when it has no were to go but jack the threads out the block.
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Very well put. The threads in the block and on the stud form a 60 degree inclined plan, causing the hole in the block to be expanded outwards. This can cause cracks in the block between the head bolt hole and the water jacket. Once the water starts to leak into the bolt hole, the integerity of the stud will be compromised over time. When the head stud is not bottomed out the force is more vertical, because the nut is pulling the stud straight up. This is mainly where a stud can exert more clamping force then a bolt, before exceeding the strength of the threads in the block.

Paul
 
I had a 855 cummins that had a weeping issue at the front and back of the head, used ironite sealant and it has been holding ever since. I'm no fan of that crap, but have seen it work. If I was convinced I had a good fire seal, and was just coolant weeping I might try that.
 
I honestly don't think switching head studs will solve the problem. How many re-torques have you done? It's only seeping, so why not do a re-torque and make sure the stud isn't bottoming out, and go for 150 ft. lbs.? It's your money, do what you want, but it seems like a waste to switch studs first before checking all the other options. What happens if you switch studs and it doesn't solve the problem? Back to square one? $.02
 
This was only the second retorque, and going from 130 to 135 made a big difference in the amount of coolant leaking. That is why I thought that it may finish the job if I could get it to 160, the retorque I did brought it from a constant stream, to a very slow drip.
 
kjpcummins said:
Whats wrong with screwing the stud all the way to the bottom? They designed studs to tighten them down into the block then the nut to hold the head down. If the studs shouldnt be tighten down into the block why do they design them that way otherwise you could just hand tighten them to the bottom.
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They are designed to be stopped by the shoulder on the stud, not by bottoming out in the hole. Furthermore, the threads just need to be in the block the length of the diameter of the stud to hold its full capacity. I know that sounds crazy, but take a look at how thick a nut is. Essentially it is the same thing.
 
mondtster said:
They are designed to be stopped by the shoulder on the stud, not by bottoming out in the hole. Furthermore, the threads just need to be in the block the length of the diameter of the stud to hold its full capacity. I know that sounds crazy, but take a look at how thick a nut is. Essentially it is the same thing.
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Not even close, the cast block is way more soft than the nuts, its coarse thread (again holds less).... you want every thread you can get in the block, with out it bottoming. For educational purposes you can go ahead and screw the stud in only the length of the nut and see how well thats holds.
 
cumminsX said:
This was only the second retorque, and going from 130 to 135 made a big difference in the amount of coolant leaking. That is why I thought that it may finish the job if I could get it to 160, the retorque I did brought it from a constant stream, to a very slow drip.
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IMO if you need 160lb to stop a leak then there is something wrong..... lots of heat cycles between re-tq's and use lots of molly......i run 125lb at 80 psi of boost and holding strong ( knock on wood)
 
Joesixpack said:
Not even close, the cast block is way more soft than the nuts, its coarse thread (again holds less).... you want every thread you can get in the block, with out it bottoming. For educational purposes you can go ahead and screw the stud in only the length of the nut and see how well thats holds.
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This info is per my dad, who was an engineer in the engine development program for Deere. He did plenty of testing on head bolts, studs, and the proper installation of them for a production setting, why would he lie about it?
 
I've been thinking I may switch to studs as well (Even though the Stock bolts are holding perfect so far), cause I've got a chance to purchase a used set that were only installed for a short time....They are the ARP 2000's and for $300........Is it worth it or should I just spring for a deal on a NEW set of 625's and be done with it......Budget is key though!!???
 
mondtster said:
This info is per my dad, who was an engineer in the engine development program for Deere. He did plenty of testing on head bolts, studs, and the proper installation of them for a production setting, why would he lie about it?
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Well in this case he's dead wrong or you miss understood him. You can't compare coarse thread in cast to fine thread tool steel. Show me a head stud or bolt anywhere with only as much thread engagement as the width of the stud in the block. Sure if the block was as strong as the fastener but its not.
 
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