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Why did my 4.0L head get destroyed?

MomoJeep

MomoJeep

Basic User
City
Seattle
State
WA
Well Looks like I destroyed my 4.0L head on top of 258 block MPI Mopar conversion engine. After only 50k miles the valve seats are totally destroyed.

I think I drove it too hard. The days the valves started tapping was a hot summer day, driving all days long over mountains with a very heavy load.

Any other possible reasons for this?
 
The oiled gauze filters are terrible at stopping dust ingestion. Paper filters are about the only kind that really stops dust. Not great on performance, but great for engine life.
 
Look in your intake air duct. Should show the extent of dust/dirt migration into the system. Ran one on a WRX till I noticed how poor a job it did at filtering air. Just slightly better than running with out.
 
MomoJeep said:
Well Looks like I destroyed my 4.0L head on top of 258 block MPI Mopar conversion engine. After only 50k miles the valve seats are totally destroyed.

I think I drove it too hard. The days the valves started tapping was a hot summer day, driving all days long over mountains with a very heavy load.

Any other possible reasons for this?
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I had a very similar issue with a rebuilt SBC 350 in my step-van. Except I only got >5000 miles.

The original rebuilder (highly recommended Chevy mechanic) advised that I needed hardened valve seats in the heads. He told me the reason was the engine was running hotter than other vehicles due to the layout of the engine compartment.
Anyway, after the repairs the engine ran great for me during my 8+ years of heavy loads (on flat FL roads)

I wonder if the blocking of the 4.0 coolant passages make the heads more susceptible to heat damage. :shrug:
 
FLCJ8 said:
I wonder if the blocking of the 4.0 coolant passages make the heads more susceptible to heat damage. :shrug:
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Good question. In the back of my head, I wondered about that too. It seemed many people were doing this conversion so I kinda assumed it was OK. Since the 258 head doesn't have those same passages, I wonder if there is some other mechanism by which the 258 head runs cooler and doesn't need them!?

And.. Should I then consider a 258 head with some performance upgrades over a 4.0L head?
 
Found this old thread from 2012... I don't know a lot about engines/valves. How does installing those chevy valves make a difference?

rguest3 said:

spankrjs,

Correct with just the 4.0 HO head swap you would get an increase of 20-40 HP. But with a good combination of Cam, Heads, Intake, Headers and Carb with proper block machine work done the HP levels can be doubled. Remember the stock 258 with Carter carb is in the 110-120 HP range. 200HP is not a stretch at all for a 258 cubic inch motor. If done correctly the torque numbers will increase very nicely as well.

The other option is to machine the 258 Head and install 1.94, 1.50 chevy valves. Seems to wake up the stock head quite well.
 
In for responses. I moved my extra engine from one spot to another this weekend, but plan on eventually building it and swapping it into my green '7. I was debating a head swap while I had it apart.
 
wm69 said:
In for responses. I moved my extra engine from one spot to another this weekend, but plan on eventually building it and swapping it into my green '7. I was debating a head swap while I had it apart.
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What I think I've learned about the head swap is: I'm not a big engine guy. And as soon as you veer away from stock, I think you really need to understand engines and custom engine building. (I don't!). I've already know how mods to other parts of the vehicle can make things more complex. For me, with engines, I want to stick to reliability and straightforwardness. The builder in my area is telling me I should have "degreed" my cam when the RV cam was swapped in along with my head swap. I don't even know what that means. I have no idea why my head started to die after 30k or so. It's a mystery I don't know how to figure out. So my advice is either really know what you are doing, or have a really knowledgable shop do your swap.
 
It would be good to know how your head failed. Was it just the valve seats and which one? Exhaust or intake...Or was it both. How do the pistons look. If there is no smoking gun and you decide to rebuild. Have the shop spec out the parts so you see and understand what is being installed. It is frustrating to lose an engine. For myself I would strive to understand what the root cause is so it can be addressed and not be repeated.
 
Degreeing the cam is a good thing to do, especially when installing a non-stock cam. It basically allows you to double check the opening/closing events, valve lift and duration against the cam card. I've only degreed one, but found it both an interesting and educational process.

I'm definitely not an expert, but curious about the valve springs on the destroyed head- was it a stock set up, or had they been replaced? I wonder if they were too weak and allowed exhaust gasses to slip past and hasten the degradation? Might be good to remove one or two of those springs on the badly damaged valves and test the compression. Just spit balling here in tracking down a culprit...
 
jpnmaine said:
It would be good to know how your head failed. Was it just the valve seats and which one? Exhaust or intake...Or was it both. How do the pistons look. If there is no smoking gun and you decide to rebuild. Have the shop spec out the parts so you see and understand what is being installed. It is frustrating to lose an engine. For myself I would strive to understand what the root cause is so it can be addressed and not be repeated.
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I think it was the exhaust valves, on all cylinders..
 
The exhaust valve seats have recessed so far, there is now only one of the three angles! This is the case on all cylinders..
 

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The head can be rebuilt. Valve lash comes to mind as well as valve spring tension as mentioned above. I am not a builder, but a good engine builder probably could put a finger on the issue.
 
I haven't built anything other than a LOT of Honda ATV engines. I wasn't planning on doing anything big. Let's face it, if you want HP an LS is the way to go.

I just always take the approach that if I'm tearing something down anyway, I might was well do bolt on upgrades (if they're worth it).

What all did you do to this engine? Doesn't sound like it was just a head swap.
 
One of our local 4x4 shops (4x4 Land) is owned by Mike Starkbaum (scrangler on this board). They posted on facebook that they have 6-8 "pulled running" 4.0s that range from 600-1000 each. Just food for thought.
 
tower210 said:
One of our local 4x4 shops (4x4 Land) is owned by Mike Starkbaum (scrangler on this board). They posted on facebook that they have 6-8 "pulled running" 4.0s that range from 600-1000 each. Just food for thought.
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Thanks! Is that in the Kansas area? Any idea how much it costs to ship an engine to Seattle?
 
MomoJeep said:
Thanks! Is that in the Kansas area? Any idea how much it costs to ship an engine to Seattle?
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not sure....but you might be lucky depending on your urgency. Pretty sure Mike has family out there now (Oregon?). Usually flies; but you might catch if he had to drive a trip.
 
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