Popped another headgasket

I've got mine set at 125 and I re torqued them 5 times.
They've held for almost 2 years at 75psi and 4000rpms.

Cliff, I think that something isn't flat there buddy. Should have held unless your drive pressure is wicked high. I have seen a gasket with studs blow at only 50psi of manifold pressure. He was making over 90psi of drive pressure though with his homebuilt twins......not cool.

I really wouldn't recommend torquing them more than the ARP specs. I have a feeling that they know a hell of a lot more about fasteners than any of us do.

Gus is right, make damn sure that all the surfaces are clean. Really clean.
Good luck!
 
well the new tq wrench is brand spanking new from snap on facny eletronic one that i payed to much for but oh well so that isnt goign to be a big issue. ive cleaned her up real nice like and had to go buy a cherry picker and mess with that for to long just to realize that i dont have a chain :bang and have to wait till tommrow to get one, sigh still got the rest of the week i guess, good news is cross thatchin is still there along with the pistons looking great after 4000+ rpm.
 
You can take them over the recommended spec but you better make sure that you use moly and pull them down on long smooth strokes. The studs in my 6 speed are at 130 and she's doing fine.
 
J.Keith said:
I've got mine set at 125 and I re torqued them 5 times.
They've held for almost 2 years at 75psi and 4000rpms.

Cliff, I think that something isn't flat there buddy. Should have held unless your drive pressure is wicked high. I have seen a gasket with studs blow at only 50psi of manifold pressure. He was making over 90psi of drive pressure though with his homebuilt twins......not cool.

I really wouldn't recommend torquing them more than the ARP specs. I have a feeling that they know a hell of a lot more about fasteners than any of us do.

Gus is right, make damn sure that all the surfaces are clean. Really clean.
Good luck!
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Please explain to me how 90psi will blow a head gasket.
 
GFB said:
Please explain to me how 90psi will blow a head gasket.
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Don't know for sure if I can. But I do know that once we got his drive pressure in line with his boost pressure all was fine. I don't think that 90psi alone will pop the gasket. I think that is is a combination of the improper balance of wastegating thus creating a exorbitant amount of drive pressure. Thus it's not the 90psi but rather the compounded backpressure and cylinder pressure and heat. I have little doubt that a properly setup system would hold well over 100psi of boost on o-rings and studs.
 
Someone want to explain to me what the difference between drive pressure and boost pressure is, or is that the same thing, different name?
 
Boost pressure is the intake manifold pressure.
Drive pressure is the exhaust manifold pressure.
 
So lets say 90 psi drive pressure--then there's 90 psi in the cylinder during the exhaust stroke. There is no compression of this 90psi air, like during the compression stroke. All it is, is 90psi. That's it. When the Exhaust valve closes there is still 90psi in the cylinder, but only for that brief moment at and after TDC (assuming overlap). The piston then starts the downward stroke, increasing cylinder volume and taking in charge air at manifold air pressure. The charged intake air is the only volume ever compressed, and at 16:1 or whatever comression ratio, combined with the forces exerted during the combustion event, is a heck of a lot more stress on the gasket than 90 psi.

I'm not trying to downplay anybody's intelligence or their understanding of how an engine works. It just doesn't make sense to me when people bring up the "excess drive pressure blows headgaskets" adage.
 
Gotcha. I didn't realize that the turbo was that much of a "choke" on the exhaust!
 
GFB said:
So lets say 90 psi drive pressure--then there's 90 psi in the cylinder during the exhaust stroke. There is no compression of this 90psi air, like during the compression stroke. All it is, is 90psi. That's it. When the Exhaust valve closes there is still 90psi in the cylinder, but only for that brief moment at and after TDC (assuming overlap). The piston then starts the downward stroke, increasing cylinder volume and taking in charge air at manifold air pressure. The charged intake air is the only volume ever compressed, and at 16:1 or whatever comression ratio, combined with the forces exerted during the combustion event, is a heck of a lot more stress on the gasket than 90 psi.

I'm not trying to downplay anybody's intelligence or their understanding of how an engine works. It just doesn't make sense to me when people bring up the "excess drive pressure blows headgaskets" adage.
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Not gonna argue with you on that. All I can base my opinions on is what I've seen and done. Everytime that I've seen a truck running a lot of drive pressure it has never been long before the headgasket popped. Thats why I run a drive pressure gauge on mine all the time. I watch it more than the boost usually.
 
LostnWalmart, what have you done to the valvetrain to hold up to those 4100 rpm Adrenaline runs? Just curious because you said the pistons looked good so whatever yours has must be working.
 
got some 110 lb behive springs from greely automotive machine and a fluid dampner to keep the harmonics down, oalso guys got her running tonight and i think i fixed that hard starting issue i was having....
 
well was torqueing the head down for the 4th time broke the nuts loose re applied moly and took them from 130 to 140 and all was going good until i had one stud break off AKKKKK, im was able to get it out and im going to cummins tomorrow to get a regular bolt until i can get a new stud, this set has been used and reused about 3 or 4 times with multiple tourqueing each time think there to fatigued and i need a new set?
 
The same set I've had for over 3 years and they have been on and off a total of 4 times and pulled to 130 every time without a problem are still working great in my 6 speed truck. When going above 125 you need to use long smooth pulls.
 
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