I think my head gasket failed

[mgFray]

For future reference the casting number on my heads is 10137567 which appears to correlate to the AM General 5743222 in a parts compatibility chart I found. (Which is what I expected, as 5743222 is the AMG part they offer.)

So it appears that the ProMAXX CHE856N is what I do need (angled bolt holes). The casting is Chinese, but the machining and finishing was done in the US (from what ProMAXX said). But for $529 each (shipped) vs $1600 from AMG.. Seems like a reasonable tradeoff.

Unless someone here knows why I should go this way, I'll order them tomorrow. Thanks for all of the help!

 

[MarkM]

Good luck with the swap. It looks like a viable and cost effective way to go. Please keep us updated.

Mark

 

[87cr250r]

Did you have an obvious blow-out in the head gasket? Cracking between the valves is essentially normal for these engines and I don't think it is detrimental. I think that relief cut in the face of the head is there to encourage cracking to occur in that area. The guys repairing them are using stitching pins. This seems like a good idea as the cracking stress relieves the head and the stitch pin stabilizes. Never accept a weld repair.

 

[mgFray]

Did you have an obvious blow-out in the head gasket? Cracking between the valves is essentially normal for these engines and I don't think it is detrimental. I think that relief cut in the face of the head is there to encourage cracking to occur in that area. The guys repairing them are using stitching pins. This seems like a good idea as the cracking stress relieves the head and the stitch pin stabilizes. Never accept a weld repair.

There is signs that the gasket itself may have failed.. but it's a 'may have'. But I definitely have coolant in the exhaust, and exhaust into the coolant. There are no signs of cracks in the engine/cylinder walls.

The heads were brought to a machine shop for inspection, and they found cracking all the way into the valves. The shop says they have welded/repaired them before, but they can not guaranty the repair due to the nature of it. They have not proceeded to pressure test the heads yet, until I decided to repair or replace (or let them be). At present I'm leaning toward the replace, as the shop quoted $600 a head to repair, replace the valve seats, and pressure test everything. A new head (shipped) is around $530 (casting Chinese, machining/assembly USA). That should be fine, and externally nobody will be able to tell the difference.

 

[87cr250r]

The part that makes me leery of the aftermarket heads are the pre-cups. It's a very special material, I think Nimonic 80. I don't believe the Chinese pre-cups are cast from the same material.

I don't have any experience with aftermarket heads so I can't share anything beyond this.

 

[mgFray]

The part that makes me leery of the aftermarket heads are the pre-cups. It's a very special material, I think Nimonic 80. I don't believe the Chinese pre-cups are cast from the same material.

I don't have any experience with aftermarket heads so I can't share anything beyond this.

ProMAXX claims they remove the chinese pre-cups as part of their machining and then once complete, installs new ones. (Pictures show the markings in the right place for the GM ones). But I'll see when they get here. If they don't look right, I can still take them to a machine shop and have the GM ones installed.

 

[87cr250r]

The GM pre-cups are smooth on the interiors. Here is a pic of the inside of some Amazon units.

 

[TOBASH]

For $2-3K you can purchase P400 heads for that GEP.

Newer cups have a more diamond shaped shape.

 

[mgFray]

For $2-3K you can purchase P400 heads for that GEP.

Newer cups have a more diamond shaped shape.

Ya, that cost is exactly what I was trying to avoid. It was $600-$1200 for a shop to fix them, or $1000 for me to try the ProMAXX heads that seems to have a reasonable set of reviews (some bad, mostly good, almost all 'good enough for the money'). The heads should be here Friday or Monday then I can look them over when I bring them over to the shop to get installed.

The HMMWV has been a money pit (knew that going in), but I thought it was behind me. I'm hoping this is the last big expense until maintenance this summer.

 

[87cr250r]

I am currently installing a 2004 vintage 6.5 engine in my CUCV. I bought it sight unseen on eBay. I'm guessing it has 100-150k miles. I pulled the heads to renew gaskets and there was valve recession and cracks. American Cylinder head in Oakland CA installed pins in the cracks. They seemed confident in their work.

The bigger problem was the top deck of the block as pictured above. That took 0.011" of milling to address. There were no signs the gasket was leaking but the same wear caused my 6.2 to fail and I wasn't going to take the chance. I put Cometic 0.56" head gaskets in to make up for the lost deck height and without a fire ring the gasket will hopefully prevent that wear. If you do go the Cometic route you'll have to specify a maximum surface roughness as they are very sensitive to finish.

Hopefully I'll have it running soon so I can report back.

 

[SmartDrug]

Ya, that cost is exactly what I was trying to avoid. It was $600-$1200 for a shop to fix them, or $1000 for me to try the ProMAXX heads that seems to have a reasonable set of reviews (some bad, mostly good, almost all 'good enough for the money'). The heads should be here Friday or Monday then I can look them over when I bring them over to the shop to get installed.

The HMMWV has been a money pit (knew that going in), but I thought it was behind me. I'm hoping this is the last big expense until maintenance this summer.

No judgment as we all have budgets for things, but those P400 heads are THE heads to get for the 6.5. If you have the possibility of Chinesium heads working for $1,100 + the time to install or $2,500 for an upgraded component that you know will work the first time and not necessitate you taking this all apart again, my money would go the expensive route, but that’s me. Buy once, cry once.

 

[Mogman]

No judgment as we all have budgets for things, but those P400 heads are THE heads to get for the 6.5. If you have the possibility of Chinesium heads working for $1,100 + the time to install or $2,500 for an upgraded component that you know will work the first time and not necessitate you taking this all apart again, my money would go the expensive route, but that’s me. Buy once, cry once.

Who is selling P400 heads?

 

[SmartDrug]

For $2-3K you can purchase P400 heads for that GEP.

Newer cups have a more diamond shaped shape.

Who is selling P400 heads?

??

TOBASH’s guy?

 

[Mogman]

For future reference the casting number on my heads is 10137567 which appears to correlate to the AM General 5743222 in a parts compatibility chart I found. (Which is what I expected, as 5743222 is the AMG part they offer.)

So it appears that the ProMAXX CHE856N is what I do need (angled bolt holes). The casting is Chinese, but the machining and finishing was done in the US (from what ProMAXX said). But for $529 each (shipped) vs $1600 from AMG.. Seems like a reasonable tradeoff.

Unless someone here knows why I should go this way, I'll order them tomorrow. Thanks for all of the help!

I do not see why the "normal" or "angled" heads would have a different casting number, it is ONLY the angle the intake bolt holes are machined to that are different, the NA takes the straight or "normal" holes, if you look at your heads, the intake bolt holes are at 90 deg to the gasket surface or not.

 

[Mogman]

Stick an intake bolt in your head I bet it does not look like this if it is an NA engine.

 

[TOBASH]

??

TOBASH’s guy?

Will L on The Hummer Network can answer that question.

 

[T9000]

Stick an intake bolt in your head I bet it does not look like this if it is an NA engine.
View attachment 891663

What is the smaller rectangular opening next to the bolt for? I understand that the other four (only three shown in this picture) provide the cylinders with air, what is the function of the fifth one?

 

[Mogman]

What is the smaller rectangular opening next to the bolt for? I understand that the other four (only three shown in this picture) provide the cylinders with air, what is the function of the fifth one?

That is an exhaust crossover port, not used on this application so it is simply blocked off, another throwback to its gasoline roots.
In its gasoline ancestors it would be routed to the base of the carburetor to prevent carb icing and pooling of raw gasoline in the manifold.
Come to think of it that is why you were seeing exhaust coming out of your loose intake manifold.
That "hole" or port is connected to one of the exhaust ports.
EDIT, that port is used on the 6.2/6.5L engines with EGR, that is where the EGR valve picks up the exhaust on the civy models to route exhaust into the intake.

 

[87cr250r]

The C code engines connected the ports left to right bank in the intake manifold. It helps reduce the exhaust drone sound at certain engine speeds. The C code engines also had a muffler before the air cleaner.

 

[mgFray]

Stick an intake bolt in your head I bet it does not look like this if it is an NA engine.
View attachment 891663

Well I orderered the angled one. So if it's wrong, I guess I screwed myself and will have to pay to return them. We'll find out when they show up. I don't have the heads, they're at a machine shop somewhere else with the shop doing my work somewhere else. So if it's wrong, I'll have to eat the shipping to return them and buy the right ones.