Keep cracking heads

[nolaninblaine]

1991 7.3. Has head studs, 110cc pump and a hypermax based turbo kit. Truck makes 20-24 psi. It rips pretty good.

The problem im having is that i keep having the heads crack between the valves. Im getting ready to tear it down for the 3rd time in the last year.

This last time it only took about 20 miles. Hadn’t towed with it yet, just driving back and forth to work.

The cooling system is all new with exception of the radiator.
Water pump, fan clutch, motorcraft t stat… all new.

Has anyone had this kind of problem over and over again? It’s getting kinda spendy

 

[The_Josh_Bear]

Welcome to the forum, and sorry to hear about this issue. That is no fun at all. Sorry to say I can't help directly.

Could be that the heads you put on are already cracked. I've never done it, but I've read about getting used heads magnafluxed before installing. Did you?

I have been reading about these engines a long time, can't say I've seen many threads about cracking heads from turbo use.
What's the symptom/s?
Is it cracking in the same place?
How particular are you about your head stud torque and pattern?

 

[nolaninblaine]

All the heads ive been through have all gone to the machine shop first for valve job and surface. They inspected them while they are apart. Very meticulous machine shop. I used to work there years ago.

Head studs are torqued exactly how arp says to do them. I never have head gasket problems.

I installed a mechanical temperature gauge (truck still runs) and even with it pushing compression into the cooling system, it stays at exactly 180. I did switch to a 7lb cap though. Not sure what the temps were before that. I have a new 4 core radiator on the way. Im sure mine is still in goo condition but im willing to try anything.

 

[lotzagoodstuff]

+1 with JoshBear on the fact that you have an odd issue. IDIs do a lot of goofy stuff, but cracking between the valves isn't very common. One additional question: is this issue happening on the same head(s), or have you swapped heads only to have a different head crack in a similar place?

Either way, it's an odd problem. Nothing but respect for you ripping it down a third time to keep your bricknose on the road with boost.

 

[nolaninblaine]

They are different heads that i have bought used, and had rebuild. I have thought about having the cracked ones drilled and pinned. But i don’t know how long it would last. Has anyone tried it between the valves?

It does seem to always be on the drivers side.

One think i am going to change when i have it apart, the egt sensor is on passenger side maybe 3-4” past the collector in the up pipe. I think im going to drill and tap the drivers manifold and put it there. Would be interesting if one bank was running muvh hotter than the other.

I am also still non inner-cooled. I dont let it get north of 1,100. But I thought that trashed pistons, not heads.

 

[Dirtleg]

They are different heads that i have bought used, and had rebuild. I have thought about having the cracked ones drilled and pinned. But i don’t know how long it would last. Has anyone tried it between the valves?

It does seem to always be on the drivers side.

One think i am going to change when i have it apart, the egt sensor is on passenger side maybe 3-4” past the collector in the up pipe. I think im going to drill and tap the drivers manifold and put it there. Would be interesting if one bank was running muvh hotter than the other.

I am also still non inner-cooled. I dont let it get north of 1,100. But I thought that trashed pistons, not heads.

At that boost level, you need an intercooler. Very hot air entering the combustion chamber.

I don't know specifically that is contributing to you problem, but just in general practice it'll give you better overall performance.

 

[nolaninblaine]

Its in the works. Would have happened in the next week or two if the truck would quit breaking it’s self.

 

[Jesus Freak]

Look up the "6.9 cooling mod", @IDIBRONCO suggest it a bunch. They capped a couple of the water ports on the 7.3 heads that cause them to run a bit warmer than the 6.9. It's not much, but more than nothing.

 

[hacked89]

All the heads ive been through have all gone to the machine shop first for valve job and surface. They inspected them while they are apart. Very meticulous machine shop. I used to work there years ago.

Head studs are torqued exactly how arp says to do them. I never have head gasket problems.

I installed a mechanical temperature gauge (truck still runs) and even with it pushing compression into the cooling system, it stays at exactly 180. I did switch to a 7lb cap though. Not sure what the temps were before that. I have a new 4 core radiator on the way. Im sure mine is still in goo condition but im willing to try anything.

Which brand 110cc pump is this? You are saying your cooling temp sensor and gauge stay exactly at 180 no matter the condition? No fluctuation? Even going up a grade? I have my truck setup running cool and no cooling mod 130cc pump. IDIs can run up to 230f comfortably. But you shouldn’t have exactly 180f under all conditions. I consider that no temp gauge if that’s the case. Did you also put comp910 springs or something that increase seat pressure?

 

[nolaninblaine]

Pump was from classic diesel. Still running stock valve springs. The temp gauge is a vdo mechanical unit. I installed it after i changed the head out the last time and after a few miles heard bubbles in the reservoir when i shut the truck off (damage done). I haven’t towed with it yet.

 

[nolaninblaine]

Not running any cooling mod. But ill look into it. I ordered a 4 core aluminum radiator thinking maybe mine is plugged. But i dont think it is. Ill still change it though

 

[u2slow]

My experience with cracked IDI heads is something is a problem in the cooling system.

I worked at one shop where the old machinist had come up with a hacky fix that worked well. (Chev diesel heads for sure, and i *think* 6.9/7.3 also.) He would bore out the cooling passage between the valves, slightly, and sleeve the passage with a valve guide.

 

[nolaninblaine]

My experience with cracked IDI heads is something is a problem in the cooling system.

I worked at one shop where the old machinist had come up with a hacky fix that worked well. (Chev diesel heads for sure, and i *think* 6.9/7.3 also.) He would bore out the cooling passage between the valves, slightly, and sleeve the passage with a valve guide.

Any pics of this? I need a visual. Ill try some googling

 

[u2slow]

Any pics of this? I need a visual. Ill try some googling

Sorry no.... that was 20-25 years ago.

I googled up a head, and put on arrows where i think the valve guide gets pressed in. Like i said, i could be wrong and this was a 6.2/6.5 only trick.

 

[Black dawg]

Have you had the heads checked to see if the cracks are actually leaking. Have seen many cracked there that don't leak. Have seen a couple blocks leak, one pinholes, and the other had a slightly loose fitting sleeve that. Was inside the fire ring