Why did my 4.0L head get destroyed?

[CJ-8_Jim]

Decision made:

Bottom end is good, so... New lifters plus this head (water passages welded):

https://www.ebay.com/itm/AMC-JEEP-C...ONVERSION-CYLINDER-HEAD-REBUILT-/153425170846

Just saw this post. I might be too late, but FWIW...

• I bought an eBay 4.0HO head from Clearwater Cylinder Head (which now sells on eBay as Odessa*cyclinder head) about 12 years ago for a head swap. I would not buy from them again.
  • I ordered the coveted 7120 casting head and they shipped me a head with the casting number ground off. I don't believe they sent me a 7120. As you migh know, there are many 4.0HO heads that look very similar but are different
  • It was missing the exhaust alignment pin.
  • Here is evidence that Clearwater Cylinder Head is Odessa - the images used on Clearwater's website say "Odessa*CylinderHead"): https://www.cylinder-heads.com/shop...,5927,5582,5556,5307,5033,4993,4876,4867,4751
• Only the 7120 and 0630 heads are viable for the head swap. The 0331 head is not viable -- it suffers reduced performance as a result of smaller exhaust ports (needed for improved emissions).
• The 7120 supposedly is better than the 0630, but I can't recall why.
• I no longer have the engine & head -- I have since installed a budget stroker (so much better than the Odessa/Clearwater 4.0HO head with MPI).

 

[CJ-8_Jim]

MomoJeep - I see you are in Seattle.
There is an awesome and highly affordable engine remanufacturer in your backyard Spokane: S&J Engines. https://www.sandjengines.com/

I shipped them a 258 crank which they reman and then put -it into a 4.0 block they were reman for me -- they even reduced the price of the reman 4.0 because I gave them the crank to use instead of the 4.0 crank.

 

[bigwalton]

MomoJeep - I see you are in Seattle.
There is an awesome and highly affordable engine remanufacturer in your backyard Spokane: S&J Engines. https://www.sandjengines.com/

I shipped them a 258 crank which they reman and then put -it into a 4.0 block they were reman for me -- they even reduced the price of the reman 4.0 because I gave them the crank to use instead of the 4.0 crank.

You should post about this separately, a new thread in this same subforum. This sounds like something a lot of folks would be interested in knowing and good engine shop recommendations are great to have. I know I'd never heard of them.

 

[jmarkel]

I don't know...something isn't adding up here. I did my 4.0L head conversion in 2002. I got the head from a junkyard, and took it to my local napa to regrind the valves and seats and face it. the ODO on the cherokee i took it from was 149k. I used marine tex gray in the water jacket holes, and added a clifford intake, borla exhaust, and topped it with a weber carb. I ran it that way for about 35k miles and then swapped the weber over to a howell tbi (another 25k). at the 90k mile mark the engine had a lot of blowby, so I did a rebuild (cylinders were out of round). when I pulled the head the valves and seats were perfect, so the valve seals were replaced and it was just cleaned and bolted back on. I did redo two of the water jackets as they looked questionable. And, I used THE SAME JAR of marine tex grey i still had from 2002. That was this past summer. Now, i had some issues with what the jacknut did with the motor rebuild I had to address, but it doesn't take away from the fact that the head needed basically nothing after running for 60k.

One thing I am very meticulous about is carb and FI tuning. I know a lot of people bolt that weber on and just go. I ended up rejetting the weber after a lot of time invested in plug chops and exhaust sniffing. Same with my howell. I did a lot of data logging, sniffing, timing, etc and had howell reburn a chip based on my recommendation and approach to my jeep. Outside of it idling at 800 to get the right A/F, it's perfect across the whole range. I can live with the idle being up, particularly because I have an AC. I would imagine that overly rich or overly lean conditions would also adversely affect your valve train.

 

[MomoJeep]

Just saw this post. I might be too late, but FWIW...

• I bought an eBay 4.0HO head from Clearwater Cylinder Head (which now sells on eBay as Odessa*cyclinder head) about 12 years ago for a head swap. I would not buy from them again.
  • I ordered the coveted 7120 casting head and they shipped me a head with the casting number ground off. I don't believe they sent me a 7120. As you migh know, there are many 4.0HO heads that look very similar but are different
  • It was missing the exhaust alignment pin.
  • Here is evidence that Clearwater Cylinder Head is Odessa - the images used on Clearwater's website say "Odessa*CylinderHead"): https://www.cylinder-heads.com/shop...,5927,5582,5556,5307,5033,4993,4876,4867,4751
• Only the 7120 and 0630 heads are viable for the head swap. The 0331 head is not viable -- it suffers reduced performance as a result of smaller exhaust ports (needed for improved emissions).
• The 7120 supposedly is better than the 0630, but I can't recall why.
• I no longer have the engine & head -- I have since installed a budget stroker (so much better than the Odessa/Clearwater 4.0HO head with MPI).

Well damn... I order the head before I saw this. After having it installed there is a misfiring issue. Mechanic checked everything else, and thinks it's either a bad valve guide or bad spring(s). This is really frustrating because when I buy something I expect it to be good, and that's about 5 hrs of mechanics labor wasted putting it on, now taking it off again to see what's wrong with the head. I'd almost rather have found a used head in a junk yard and started from scratch. The head is at the rebuilding shop now, and if indeed it has issues, I'll be calling Clearwater/Odessa and expecting them to make good, of course! I'll keep ya'll posted.

NOTE: Having two Jeeps used to seem crazy to me. But I miss my Jeep a lot since it's been down for two months now!

 

[MomoJeep]

Update: Rebuilder says the head was shipped out with the following issues:

- Valve grinds were crappy
- After welding the water jackets, the head warps. They machine it flat where it mates the block, but the standing valve heights are still off from the warpage.
- a Bad valve guide.

 

[CJ-8_Jim]

Update: Rebuilder says the head was shipped out with the following issues:

- Valve grinds were crappy
- After welding the water jackets, the head warps. They machine it flat where it mates the block, but the standing valve heights are still off from the warpage.
- a Bad valve guide.

Sorry to hear you too had a bad experience with eBay vendor Odessa*cylinderhead (also DBA Clearwater Cylinder Head).
My experience was bad, but yours is worse.

FWIW, I never really noticed much improvement if any with a Odessa/Clearwater Cylinder Head 4.0HO head on a 258 block that already had MPI (which is the same setup you have: 258 with existing MPI).

 

[MomoJeep]

Apparently the 4.0head has better flow to the valves. I assume that only really matters at higher RPM's. I've seen claims of 25-40hp gain and a few MPG's. I have no way to measure or verify those claims.

 

[spankrjs]

Somebody with more knowledge then me could probably explain it better, and I might be wrong, but the head is only one part of the equation. Yes, the 4.0 head might flow better on paper and in real life, but only when coupled with the matching cam shaft. Also, the shorter stroke of the 4.0 vs 4.2 makes the 4.0 rev a little quicker.

I have both engines with MPI, 4.0 and 4.2. The 4.0 seems to pull a bit better at higher RPM's, the 4.2 is much stronger right off idle and low RPM's. My 4.0 bone stock, my 4.2 is bored 30 over with a very mild RV cam.

I have no experience with a 4.0 head on a 4.2. I just never saw the cost/benefit pay out, just my opinion though. I could be missing the boat, so to speak?

 

[CJ-8_Jim]

Somebody with more knowledge then me could probably explain it better, and I might be wrong, but the head is only one part of the equation. Yes, the 4.0 head might flow better on paper and in real life, but only when coupled with the matching cam shaft. Also, the shorter stroke of the 4.0 vs 4.2 makes the 4.0 rev a little quicker.

Agree. For example, intake and exhaust are also part of the equation.

Beginning 25 years ago in the late 1990s, there was a lot of 4.0HO headswap hype starting through the mid-2000s (i.e., magazine write-ups, posts at now defunct CJ forums, extensive article writeups... I think the famous "Jefe" wrote one too).

With 20/20 hindsight and 12 years more experience owning a CJ and a wrench, I think all the 4.0HO headswap hype with reported gains of 25hp-40hp was in comparison to the OEM carburetated 258 with all its 1980s emissions equipment. Not in comparison to a 258 with MPI (or any other fuel injection for that matter).

I have both engines with MPI, 4.0 and 4.2. The 4.0 seems to pull a bit better at higher RPM's, the 4.2 is much stronger right off idle and low RPM's. My 4.0 bone stock, my 4.2 is bored 30 over with a very mild RV cam.

Agree again... that's my experience too.

In addition, I would also add the stroker gives the best of both worlds and then some. I have a "measly but inexpensive" "budget" stroker now and its noticeably better than both OEM 4.0 and 258.

But that's for a different thread: Engine swap costs and benefits.

 

[FLCJ8]

In addition, I would also add the stroker gives the best of both worlds and then some. I have a "measly but inexpensive" "budget" stroker now and its noticeably better than both OEM 4.0 and 258.

But that's for a different thread: Engine swap costs and benefits.

I'm definitely looking forward to your thread
I have a ton of parts, including the 4.0, for a stroker but have had a hard time getting the latest specs for a reliable build.

 

[CJ-8_Jim]

I'm definitely looking forward to your thread
I have a ton of parts, including the 4.0, for a stroker but have had a hard time getting the latest specs for a reliable build.

Already posted: Here's my 2 cents on a budget stroker: https://www.cj-8.com/threads/4-2-with-4-0-head-or-stroker.50424/page-2#post-427346

Simply put: I had a 4.0 remanufactured but with my 258 crank. I kept it long nose with V-belt to save time swapping to S-belt. I just need a reliable engine, but didn't want to give up low end torque.

https://www.jeepstrokers.com/forum/ has a wealth of information. PM me with any specific questions you might have.

 

[FLCJ8]

Already posted: Here's my 2 cents on a budget stroker: https://www.cj-8.com/threads/4-2-with-4-0-head-or-stroker.50424/page-2#post-427346

Simply put: I had a 4.0 remanufactured but with my 258 crank. I kept it long nose with V-belt to save time swapping to S-belt. I just need a reliable engine, but didn't want to give up low end torque.

https://www.jeepstrokers.com/forum/ has a wealth of information. PM me with any specific questions you might have.

Thanks, I'll check out your post and revisit jeep strokers.
I'm in the process of getting all my things into one space to start the build.
I'll hit you up with when I have some intelligent questions.

 

[MomoJeep]

Well my engine is running again. Here's what I think killed it. Driving too hard. I had my jeep full of gear, roof rack also, three passengers, drove all day long from Utah to Wyoming in summer heat, up and down many mountains, at highway speed. That was when the "ticking" started. Probably got too hot. Also, 3.31 gears with 32" tires, maybe rpm's were on the low side.

What I don't understand is that there was no issue with the temperature that I noticed. Can the inside of an engine get hot enough to cause damage even though it's NOT overheating?

The cam lobes are slightly angled such that they are able to keep the lifters rotating. Turns out they were worn flat, so the lifters weren't operating correctly. These I6 engines are tough and durable, but I guess they can still be pushed too hard.

 

[93_Fummins]

Just a thought, but heat is only part of the issues; pressure is the other. Driving hard (high engine load) at low rpm can get an engine out of the sweet spot of efficiency and into a spot where combustion pressure spikes are very high and very rich. The high pressure at low cycle speed puts more stress on everything for a longer duration of time. I doubt the lifters were an issue; roller lifters don't rotate and do the job just fine. I would be more curious about the EGT's during your "driving too hard" situation. A rich situation and slow flame front can cause heat to soak in the exhaust pathways, potentially wrecking havoc on the valves and seats. High EGT's won't necessarily reflect through the water temp, especially if it's on a cylinder that has poor coolant flow anyway.

 

[MomoJeep]

Just a thought, but heat is only part of the issues; pressure is the other. Driving hard (high engine load) at low rpm can get an engine out of the sweet spot of efficiency and into a spot where combustion pressure spikes are very high and very rich. The high pressure at low cycle speed puts more stress on everything for a longer duration of time. I doubt the lifters were an issue; roller lifters don't rotate and do the job just fine. I would be more curious about the EGT's during your "driving too hard" situation. A rich situation and slow flame front can cause heat to soak in the exhaust pathways, potentially wrecking havoc on the valves and seats. High EGT's won't necessarily reflect through the water temp, especially if it's on a cylinder that has poor coolant flow anyway.

This all makes sense, thanks. Indeed there was valve recession up into the head. One thing though, they are flat tappet lifters, not rollers. Also, doesn't the computer MPI prevent the mixture from getting too rich?

 

[MomoJeep]

Another thought: The computer can't tell if there is a different cam installed. I wonder if the "RV" cam could have been far enough from stock to create an issue? Running to rich or hot?

 

[CJ-8_Jim]

Another thought: The computer can't tell if there is a different cam installed. I wonder if the "RV" cam could have been far enough from stock to create an issue? Running to rich or hot?

I think it is really hard to say for sure why your eBay reman head failed.

Powerplants are a system of interdependent components and the more variations introduced away from OEM (even aftermarket that supposedly meets OEM-spec but of unknown durability), the less one can relay on the extensive OEM testing that originally was performed.

However that said, the guys on Jeepstrokers.com do all kinds of mods to the 258/4.0 without issues (or at least without issues that arise so soon as yours did). And notably Russ Pottenger has spent decades turning the inline 6 AMC-lineage "tractor engine" into noteworthy competition engines: https://www.facebook.com/Bishop-Buehl-Racing-Engines-248948051907539/

You mentioned above that you thought the problem was you drove it "hard" on one trip, but I don't think one trip with 3 passengers and gear should be a problem with an operable cooling system.

Perhaps the engine failure was a "'perfect storm" of numerous small things that by themselves are not an issue but together cause a catastrophic failure in the weakest link: the eBay reman head... Or on the other hand, maybe valve-work on the eBay head just failed.

Regardless, you are able to drive your 8 again and summer is coming fast.... Life is Good!

 

[MomoJeep]

Just to clarify, it wasn't an Ebay reman. It was off a 94 Wrangler in a local yard. Then I plugged the water jacket holes with metal-epoxy and sent it to the rebuilded (50,000 miles ago). I was always skeptical of the epoxy method. They held up for 50k, with the exception of two of them allowing for the tiniest barely-noticeable leak.

The new head is a Reman from Clearwater. Not impressive. Require a lot of work. I do like that they weld the plugs, but then the head warps and they only deck where it meets the block, leaving the valve heights all messed up.

 

[CJ-8_Jim]

Just to clarify, it wasn't an Ebay reman. It was off a 94 Wrangler in a local yard. Then I plugged the water jacket holes with metal-epoxy and sent it to the rebuilded (50,000 miles ago). I was always skeptical of the epoxy method. They held up for 50k, with the exception of two of them allowing for the tiniest barely-noticeable leak.

The new head is a Reman from Clearwater. Not impressive. Require a lot of work. I do like that they weld the plugs, but then the head warps and they only deck where it meets the block, leaving the valve heights all messed up.

Sorry... my bad. I got the Reman from Clearwater (which sells on eBay under the name Odessa*cyclinder head Clearwater-Odessa relationship) mixed up with the Epoxy-plugged 94 YJ donor salvage yard head.