the 0331 head thread (help out if you have one!)

[1bolt]

Okay here's the idea everyone with an 0331 head cracked or not, take a picture of the casting marks and numbers that are on the top of the head (mostly inside the rocker valley).

We want to figure out:
A) which castings crack
B) which ones don't
C) Learn of any numbers or markings (or date codes) that identify one from the other.
D) exactly where they crack (pictures!).

The 0331 is the head that came on 1999+ Grand Cherokee and 2000+ TJ or XJ. If you have one laying around take two clear pics of each half of the top of the head like I have below (so they are close enough to make out the markings) and post them here with as much info as you know. Mileage, year, model etc.

Here's my only 0331 I think it's an 01, and I believe it to be well past 100k not cracked yet



It'll probably take a while but we should be able to get to the point where we know enough that those with a crack prone version will be able to identify it by casting date codes and such, and possibly avoid doing expensive valve work to a junker, while those with the newer non crack prone 0331's will be able to confirm they have the good one, and not spend every long trip wondering if this one will be "the one where she lets go 1000 miles from home". Or even worse spend a lot of money converting over to an older head. So before you groan and think why bother, consider you could be helping some Jeepers out.

[SilverXJ]

Here is mine. It was pulled off my 2000 XJ with 96,354 miles when oil analysis came back that I had some coolant in the oil. Wasn't enough for me to actually notice a drop in coolant level, but it was there. Could have been a head gasket or this head. Didn't want to take the chance with putting the 0331 back on so I replaced the head gasket and head. Coolant levels dropped after that. Never inspected the head that well until now. The last pics shows some kind of residue between #3 and #4.







Some kind of green residue between cylinder #3 and #4.. crack?

[Alex22]

Looks like a crack to me....but....
Might want to take it to get that small part magged to be sure, I'd also Pressure test it to be sure if it mags ok. My 0721 head had a small mark like that, It didn't show up when I magged it and it passed a pressure tested ok.

~Alex

[bratcop]

Here is mine, 2001 Grand Cherokee Laredo, 96K, gave up the ghost with a cracked piston...
I have ported and polished this head, as well as had a 3 angle valve job and I am putting it back on my stroker...It currently has no crack, and I hope it stays that way...

126[1].jpg

127[1].jpg

127[1].jpg

Sorry the pics aren't the clearest, they were taken with my phone...kinda blurry, I know, but it really is an 0331 head...

Bratcop

[1bolt]

Good stuff, thanks guys, Bratcop those pics are good enough we can make out the casting marks, one thing though there's a little three digit number along the outside of the head SilverXJ photoshopped this number into his pics, can you note yours (doesn't need to be in the picture just add it to the description if you will)?

Chris can you take an old tooth brush and a harsh chemical of your preference to that spot? The green is really wierd there, I'm inclined to agree that it's a tiny crack. Like I said when we met if you are willing to part with that head for the "cause" so to speak I can try to pressure test it, and magnaflux it if needed. You may have something unique... a crack prone one (it's certainly an early head) that is just starting to give way...

We really could use some cracked heads, pics and an autopsy or two would shed a lot of light on the subject....

As it stands the 0331 was used for 7 years and it is probably going to become hard to avoid tripping over them as more and more of the last 4.0's get retired...

It would be a shame to just scrap them because no one can tell a crack prone head from a revised one...

I think a few of us are also intrigued by the improved port design. I know I would be more than willing to use a heavilly ported 0331 on a special use project (like a 1/4 miler 2wd MJ that I want to do some day), where pulling the head wouldn't be any big deal, but I sure would prefer to use a revised casting.

[SilverXJ]

Good stuff, thanks guys, Bratcop those pics are good enough we can make out the casting marks, one thing though there's a little three digit number along the outside of the head SilverXJ photoshopped this number into his pics, can you note yours (doesn't need to be in the picture just add it to the description if you will)?

I assume that is a date code of some sort? Care to decode it?

Chris can you take an old tooth brush and a harsh chemical of your preference to that spot? The green is really wierd there, I'm inclined to agree that it's a tiny crack. Like I said when we met if you are willing to part with that head for the "cause" so to speak I can try to pressure test it, and magnaflux it if needed. You may have something unique... a crack prone one (it's certainly an early head) that is just starting to give way...

It would certainly make sense if it was a crack... it is in the right place and I was experiencing a small coolant leak. I'll eventually take a brush to it to see if it will come off and reveal something. It is quite a resilient stain as I already cleaned teh head with engine degrease.

[1bolt]

Not sure what that 3 digit number is but I don't know if it's a date code, I guess it almost has to be though. the little dots with the arrow pointers are foundry codes which I'll need to see more of to try and decipher.

Not sure what NH (Noise Harshness?) 5 (or 2 in my case) signifies or why the number would be the same on yours and Bratcop's but not on mine.

We need more heads!

[1bolt]

Plugged this effort on NAXJA trying to get some more data. If anyone else wants to try and help kick up some info there are plenty of Jeepers with 0331 experiences over on JU and Jeepforum, mallcrawlin maybe... Seems like something the Jeep comunity should have tried to do a long time ago.

[5-90]

Getting magged can get spendy, depending on the shop. A good parts house should carry a dye-check kit (by Magnaflux, in fact...) that doesn't resolve as finely as a true mag check - but will show up most cracks in most parts, even plastic. Expect the dye-check kit to go for about forty bucks, and it's reasonably simple to use.

I've been trying to collect heads for research - especially if they're cracked or warped (since I plan to saw up at least one of each head anyhow - from #2685 forward.) So, if any of those cracked heads can be "parts trained" to the SF Bay Area, we can work something out... I currently have a #2685 (last-gen 258ci) and two #2686 (1987-1990 242ci.)

For casting identifiers, the "number" is typically a "batch code" - and used to indicate a specific pattern used to make a core box. This is why the characteristics of a 7120 head cast for 1991 will be essentially the same as a 7120 head cast in 1995.

The little "clock" marks are usually used to indicate the /time/ the head was cast - but each manufacturer tends to use its own code. I've not had a chance to sort out AMC's or Chrysler's coding (and I find it odd that the most prominent "clock" has eight spots, vice the more common twelve,) but that should give an insight into the date the head was cast.

My first thought on the two-character code was a leap from the "WJ" one - thinking what model the head was slated to be used on, then we'd have "XJ", "TJ", "WJ", "WK", and "JK" - with other codes being "service replacement" heads. However, this doesn't make much sense (too much of a pain to keep straight on the production floor,) so it may answer to a casting revision of some sort - a relatively minor revision.

[seanyb505]

Dont the FSMs shed light on the codes? Or is that only build differences. I know the block will have a "B" (or something to that extent) code is the bore is slightly larger than the rest of the production 4.0s.

[SilverXJ]

There is some reference on here as to what the codes on the blocks bean that are stamped on the passenger side. However the FSM makes no mention of the head codes.

[Alex22]

Liberty engine parts (parts supplier) has a new replacement head in their catalog that is meant for the 0331 heads. I did see the price, but I'm not sure if its the MSRP or our price, It wasn't too pricey either way. It could be one of the ACH heads, it didn't give a lot of info about them and the picture was too small to see anything other than that it was a JEEP head.

~Alex

[RAPTORFAN85]

Tons of info here...

http://www.jeepsunlimited.com/forums/sh ... p?t=721472

[1bolt]

Yeah but unfortunately none of it is very oriented on figuring out what we're trying to though. I think many of us have seen that thread in the past, Chris (SilverXJ) even posted to it... We just need to get more meat than that thread was digging for.

[Muad'Dib]

Yeah but unfortunately none of it is very oriented on figuring out what we're trying to though. I think many of us have seen that thread in the past, Chris (SilverXJ) even posted to it... We just need to get more meat than that thread was digging for.

Plus its nice to populate this board with our own info