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I got a call today that said my head studs came in today(arp 12mm], im going to pick them up tom.. the guy their said that he wouldn't replace the hg if it wasn't bad.. Just want to no who all has just done the studs one at a time and if it is better that putting a new gasket in or not... Im going to get a different single turbo and 110hp injectors, and thinkin of selling my comp for the adrenaline. So that is all the fuel and boost i will be having..
 

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I was just having this chat over at compD because I'm installing my studs and twins this weekend. Anyways, a lot of guys were saying that studs aren't worth it without o-rings and to just re-torque the stock head bolts. However, IMO I wouldn't re-torque the stock bolts, maybe new ones, but not ones that have been in the truck torqued and run.

I also think though, that anytime you loosen up just one bolt on the head, you are putting a lot of stress on it and the head gasket, and are compromising both. The other problem with doing this, is that bottom tapping the holes in the block is harder when you have to do it through the head as well. So, I'm going to pull my head and install a fresh gasket while I'm in there. It just seems like the safest/easiest way to do things, and it will give me a chance to inspect the inside of the engine while I'm in there and make sure everything still looks in decent shape.

Once again, this is just my opinion. Hope this helps. A new gasket was about $100 today at the dodge dealer, so that didn't seem too bad.
Sean
 

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:agreed: :whs
first of all you should take the head get checked, deck, o ring/ fire ring and maybe a porting on the exhaust side. at the min get the head check and deck. with a new gasket and studs should hold about 50lbs but i recommend getting it o ringed or fire ring the head gasket should be replaced. what i did to my was modify a 12 valve gasket .020 over stock thickness for the my 24. it just a couple holes. that what scheild recommends. as for the studs i didnt bottom them out i ran a tap down to make sure the threads where nice a clean. i had to modify the valve cover in the front and i think that was it. make sure u use plenty of stud lube advise u buy another tube or so.

do it right first time. its no fun fixing something u fixed once. beside later on down the road u might want bigger injectors or maybe some nos:sly:

i suspect that your boost will be around 40 to 45. my dad has a stock vp, htt 57/14 with ddp 110, fass and juice with att cant get it past 35 an yes the boost limit is turn up to 50lbs. he made 436hp. in my old truck ddp200, drag comp, stock vp, fass and htt quick diesel 64 and could make 50-55lbs and i made 508hp.

remember most of time that head gaskets fail is not caused by boost pressure but by drive pressure. if you do get it check dont be shock that it need guides and seats. the 24 valve head is junk!!!!!!!!!!!!
 

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smokeyourdiesel said:
remember most of time that head gaskets fail is not caused by boost pressure but by drive pressure. if you do get it check dont be shock that it need guides and seats. the 24 valve head is junk!!!!!!!!!!!!
That is an interesting point. My personal opinion on this, is that HG failure is caused by higher peak cylinder pressures, which increase because of more expanding gases created by injecting more fuel, that is in turn being burned by the added oxygen of higher boost. However higher cylinder pressures can be caused by many things, in this case they increase the amount of exhaust volume, which leads to higher drive pressures. So its not really the drive or boost pressures doing the damage, although both are increased.

As for the other point, about getting everything o-ringed. I totally agree, personally I'm trying to get my truck back together, and I can't find a shop locally that will do it in this short amount of time. I'm going to pull my head again later this spring or early summer and have it o-ringed then. I will have it checked while I have it out though. To the original poster, if you have a little bit of time get the head o-ringed while you've got it off this time, if its within your budget.
Sean
 

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Discussion Starter #5
ok thanks for the help guys. i didn;t think you had to bottom tap the block with just the 12mm studs?? i will pay to get the head oringed if it will help me not blow a gasket as easily. but no i am only going to do what i said i was going to earlyer to my truck and nothing more, mabey an intercooler if towing egts are a consern. i also thought that the one at a time didn't sound like the best idea.
 

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I've heard it called bottom taping, you aren't really tapping any new threads. Just making sure that they are all clean and in good shape. I always do the same for new head bolts too. Yeah, with studs and o-rings you should be good up to nearly 70-80psi boost, and all the fuel that could go with it. So, with your planned set up, you will be fine, and you'll have a lot of room to grow.
Sean
 

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sstockton said:
That is an interesting point. My personal opinion on this, is that HG failure is caused by higher peak cylinder pressures, which increase because of more expanding gases created by injecting more fuel, that is in turn being burned by the added oxygen of higher boost. However higher cylinder pressures can be caused by many things, in this case they increase the amount of exhaust volume, which leads to higher drive pressures. So its not really the drive or boost pressures doing the damage, although both are increased.

not to sound like a d*** :shrug:but have u checked drive pressures using a stock turbo for instance. on a hx35 35 lbs of boost is 1:1 ratio at 45lbs it almost a 2:1 ratio. so it takes roughly 80-90lbs of exhaust pressure to spool 45lbs of boost. drive pressure is why i had to do my head stretch the stock bolts with a stock charger with a 16 exhaust housing. on my htt quick diesel 64 it was a 1:1 ratio until i 50lbs or so. at 55lbs it was about 65lbs of drive pressure. that is why most not all hg will fail on the exhaust side.
 

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Well what about this though, just for instance. I'm not an engineer so I could be missing something here, but see if you can follow my reasoning. If you are forcing Air into the combustion chamber at say 45psi, and the valve closes at the bottom of the piston stroke. You are have a given volume at 45psi. Now the piston comes up and compresses that volume at a ration of 16.3:1 in an ETC or 17:1 in an ETH So you're essentially coming up with a cylinder pressure of 733.5 psi which is more than double that of a stock truck wastegated at 18-22psi. Then add to that the injection and combustion event, and your cylinder pressures sky rocket because of the expanding gases that are driving the piston. This is why advancing the timing too much is detrimental to head gaskets. When advanced, the majority of the injection event occurs closer to TDC when cylinder pressures are highest, and the combustion occurs when the compression is higher therefore increasing the cylinder pressures even more. The end result is peak pressure in the thousands of PSI range or higher. Which makes 90 psi seem inconsequential. Also, I don't see what the exhaust would be pushing off of to cause the head to lift, its all captured within the head and the manifold. So I don't see how it could really has any effect on the head gasket. Just As the pressurized air in the intake manifold doesn't have an effect on it either until it enters the cylinder.

The major detrimental effect I can see of a high drive pressure ratio, is a large pressure gradient across the shaft of the turbo, putting it up against stresses that it wasn't designed to with stand and also over speeding. I don't have an answer as to why the head gaskets tend to fail on the exhaust side? My best guess would be because of excessive heat on the side because the exhaust manifold is much hotter than the intake manifold, and excessive heat is just another element of stress to throw into the mix on that side.

I don't think you sound like a D*** and no hard feelings, this is just what makes sense to me, but if there is something I am missing that causes exhaust manifold pressure to cause failures, definitely share, I'm interested.
Sean
 

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When you bottom tap for the studs you do cut more threads in the block. You only cut an extra three or four. Stock the threads taper out, when you bottom tap you can get more threads in the block making the studs and block able to hold more.

On the top side of the stud you'll have the same number of threads no matter where the nut is on the stud as long as you have the nut full. So if you bottom tap you can shift the whole stud deeper into the block and get a better bite.
 

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Discussion Starter #10
hum, ok a little more work than i thought but o well.. so should i go with the 12 valve gasket .020 over stock thickness like smokeyourdiesel said or just factory?
 

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Either way, you might as well do the marine gasket though, just to be on the safe side. I will be installing one when I pull my head again to have it o-ringed. Are you doing the stud install your self, or having someone else do it. I really didn't think of it as being that bad of a job personally.
Sean
 

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sstockton said:
Well what about this though, just for instance. I'm not an engineer so I could be missing something here, but see if you can follow my reasoning. If you are forcing Air into the combustion chamber at say 45psi, and the valve closes at the bottom of the piston stroke. You are have a given volume at 45psi. Now the piston comes up and compresses that volume at a ration of 16.3:1 in an ETC or 17:1 in an ETH So you're essentially coming up with a cylinder pressure of 733.5 psi which is more than double that of a stock truck wastegated at 18-22psi. Then add to that the injection and combustion event, and your cylinder pressures sky rocket because of the expanding gases that are driving the piston. This is why advancing the timing too much is detrimental to head gaskets. When advanced, the majority of the injection event occurs closer to TDC when cylinder pressures are highest, and the combustion occurs when the compression is higher therefore increasing the cylinder pressures even more. The end result is peak pressure in the thousands of PSI range or higher. Which makes 90 psi seem inconsequential. Also, I don't see what the exhaust would be pushing off of to cause the head to lift, its all captured within the head and the manifold. So I don't see how it could really has any effect on the head gasket. Just As the pressurized air in the intake manifold doesn't have an effect on it either until it enters the cylinder.

The major detrimental effect I can see of a high drive pressure ratio, is a large pressure gradient across the shaft of the turbo, putting it up against stresses that it wasn't designed to with stand and also over speeding. I don't have an answer as to why the head gaskets tend to fail on the exhaust side? My best guess would be because of excessive heat on the side because the exhaust manifold is much hotter than the intake manifold, and excessive heat is just another element of stress to throw into the mix on that side.

I don't think you sound like a D*** and no hard feelings, this is just what makes sense to me, but if there is something I am missing that causes exhaust manifold pressure to cause failures, definitely share, I'm interested.
Sean
sean,
have you heard of BMEP? Brake, Means, Effective, Pressure. It is the measurement of the cyl pressure
 

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Discussion Starter #13
well, yes and no. I am going to have our old hired hand show me how to do it, he use to be a mechanic for 20+ years and has overhauled diesel motors before so he will be able to show how to do everything. where would i have to order the marine gasket from??
 

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aaronisapayne said:
well, yes and no. I am going to have our old hired hand show me how to do it, he use to be a mechanic for 20+ years and has overhauled diesel motors before so he will be able to show how to do everything. where would i have to order the marine gasket from??
Heres the one I used I also got one from Scheid awhile back (which arrived a little tweaked :nunu: )
 

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diesel jeep said:
sean,
have you heard of BMEP? Brake, Means, Effective, Pressure. It is the measurement of the cyl pressure
My understanding is that BMEP is a theoretical comparison of engine pressures and does not actually correlate to the actual cylinder pressures. The calculation for BMEP is 150.8(torque in Ft.lbs)/displacement in C.I. This offers a formula to compare two engines, but does not give an actual cylider pressure.

http://www.epi-eng.com/ET-BMEP.htm

I was working on my head with a CAT mechanic, and was having this discussion with him. He said in some of their applications they see peak Cylinder pressures reaching almost as high as 55,000 psi. I'll see if I can get further verification on that number or any CAT literature about it, because that seems really high. Anyways, that the pressures being exerted by the combustion event, and compression far out weigh any manifold pressure.

Sean
 

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aaronisapayne said:
well, yes and no. I am going to have our old hired hand show me how to do it, he use to be a mechanic for 20+ years and has overhauled diesel motors before so he will be able to show how to do everything. where would i have to order the marine gasket from??
Either Haisley or Schied diesel should have them for you. Or you could order it from a cummins parts dealer. but often times those are kind of far driving distance. Well at least you have help doing it, and you don't have to pay shop rates to have it done.
Sean
 

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Discussion Starter #17
i had to modify the valve cover in the front and i think that was it. make sure u use plenty of stud lube advise u buy another tube or so.
why did you have to mod the valve cover and what did you do??
 

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sstockton said:
My understanding is that BMEP is a theoretical comparison of engine pressures and does not actually correlate to the actual cylinder pressures. The calculation for BMEP is 150.8(torque in Ft.lbs)/displacement in C.I. This offers a formula to compare two engines, but does not give an actual cylider pressure.

http://www.epi-eng.com/ET-BMEP.htm

I was working on my head with a CAT mechanic, and was having this discussion with him. He said in some of their applications they see peak Cylinder pressures reaching almost as high as 55,000 psi. I'll see if I can get further verification on that number or any CAT literature about it, because that seems really high. Anyways, that the pressures being exerted by the combustion event, and compression far out weigh any manifold pressure.

Sean
in the past i have used BMEP to tune big Coopers. We use a gauge to measure each cyl BMEP but this is on 8700hp 20 cyl engines. The gauge cant read the actual pressure because its too high but it is reduced to a lower pressure that a gauge can read.
 
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