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Joined the "0331" club- now what?

jfs3674

NAXJA Forum User
Location
el paso tx
I recently had the honor of joining the cracked cylinder head club. So the question is, now what? I searched the forums and came to the conclusion that a replacement "0331" is a waste of money. I also learned a "0630" and a "7120" head is a good replacement. I told my mechanic/friend this and he talked to his sources. He came back and said a "7120" will not fit. I printed up a couple of threads from here pertaining the "7120".
I'm leaning toward the 7120 simply because of the availability on the web. Besides the rail for the coil pack, what other modifications are needed to drop in a 7120?
BTW I have a 2000 jeep classic w/ 4.0, AW4 and 120K. Thanks in advance.
 
The '7120' should have the dowel pins for location, like the 0331. The '0630' doesn't. It will still fit, but you have to align the head by eye with the bolt holes. The '0630' will have a temp sensor that needs plugged. The exhaust ports are a bit bigger. If you have the cast iron exhaust manifolds, they won't or will barely cover the exhaust ports on the '7120' or earlier heads. You will then need to think about a header.
Tom
 
i was under the impression that the 0630 was a direct bolt in except for the the coil pack rail (which somebody on here made brackets for. do a search). i was also under the impression that the 7120 will take a lot more work to massage into place, mike
 
sjx40250 said:
"cast iron" exhaust manifolds --Never were produced for the 4.0L and there is only one exhaust manifold.
I have two sets in my garage. I think one of them came from a '00 XJ and the other from an '03 GC. I'll have to check if I have a picture of one of them.
The 7120 is the same space as the 0630. All 4.0 heads will fit on all 4.0 blocks. I do have a 0630 on an '03 block.
Tom
PS: I do have a picture of the CI exhaust manifold on an '03 4.0L. If someone PM's me with an e-mail address, I send them them so they can post them.
 
Last edited:
Year............Casting No
1987-90......2686
1991-95......7120
1996-99......0630
2000-01......0331
Here's the numbers from Dino's page. I had the 0630 and the 7120 flipped around. The 0630 should have dowel pins to locate the head. Both have the same intake and exhaust ports. The 7120 doesn't have the dowel pins. It also has an additional temp sensor on the driver's side. I put a 7120 on an 03 block. Others have done the same (check Dino's site). I think I am the only one who had problems. I had to grind a bit in the casting near where the dowel pin are. Castings do shift core, so they aren't exactly the same. Sorry for any confussion.
Tom
 
bzzzztt! Cast exhaust manifolds came on 00+ Xjs, basically anything with the 0331 head design. I ditched the cast manifold with my 0331 head.

George T.
00XJ


sjx40250 said:
"cast iron" exhaust manifolds --Never were produced for the 4.0L and there is only one exhaust manifold.
 
Well, I finally got my 7120 in. First off, I cannot believe the difference in the weight between the two. The 0331 is about half the weight of the 7120. I do need to find a exhaust manifold to fit the 7120, the old cast iron one from the 0331 will not fit. I'll try to get some pics up. By the way, thanks for the replys.
 
jfs3674 said:
Well, I finally got my 7120 in. First off, I cannot believe the difference in the weight between the two. The 0331 is about half the weight of the 7120. I do need to find a exhaust manifold to fit the 7120, the old cast iron one from the 0331 will not fit. I'll try to get some pics up. By the way, thanks for the replys.


What are your plans for the coil rail? Planning on making your own mounts (like someone else that has fabed their own). Is it possible to drill/tap the holes for the coil rail or is that a bad idea.
 
jxj said:
What are your plans for the coil rail? Planning on making your own mounts (like someone else that has fabed their own). Is it possible to drill/tap the holes for the coil rail or is that a bad idea.

Nothing to drill and tap into unless you want to go into the engine wall. Remember the 2K+ engines had bosses cast into them.

Here's the link on the coil rail mounts I made http://www.naxja.org/forum/showthread.php?t=98206&page=2&highlight=aluminum

See post 19.
 
Well, we finally finished the install. The 7120 and matching exhaust is now on. I did have to get some custom exhaust work done, the 0331 had two exhaust outlets, the 7120 exhaust has only one. Everything seems to be running good. I did run into some problems. First off I need to fab up the coil brackets, just like the link above. I also now have a "tapping" on acceleration. The oil gauge is now reading 40 just with the ignition on. When it is on, it reads 80. Where is the connection for the oil gauge? I'm thinking its dirty or something. Overall, heres my cost-
7120 head -$230, exhaust manifold- $50, custom exhaust work $75- new gasket set- $60 and mechanic friend $150, he only wanted $100, but I gave him an extra 50. The knowledge I gained from watching and helping him is unreal. I'm pretty sure I can do this on my own now. Thank you guys for all of your information as well-
 
great now you don't have to worry about it cracking again unless you get it as hot as chernoble in russia!
 
I recently discovered this potential problem, and found out I too have that particular head casting. While I currently have no symptoms of a crack or leak, I am concerned.

My Wrangler is a 2000 model (build date 10/99) with 70+K miles thus far. Are these heads doomed to failure or is it really a pretty spotty failure?

Can it develop a crack without any problems or symptoms, or does a crack automatically equal a leak - no 'in-betweens'?

Thanks for your help folks,
Jim
 
Jim,
They all don't crack. But with that milage you are closing in on the milage that I have seen a few crack at. I'd keep an eye on your coolant level. If you start to loose coolant, look at this problem. If you ever have this problem get it repaired quick as possible. The two or three cases I have seen, the people ran the engine for a few months that way. It took out a cam lobe on one and possible the bearing on the other. But the bearing were good on the one the cam was wiped out on.
Tom
 
Jim Cissell said:
I recently discovered this potential problem, and found out I too have that particular head casting. While I currently have no symptoms of a crack or leak, I am concerned.

It seems to be hit-or-miss (typically falling on the 'miss' side) for whether or not it happens. I've got 115,000 miles on my 2000 with no problems, and had about the same mileage on my totalled 2001 - also with zero issues. See this thread for further thoughts on the 0331 head issue.
 
I had just become a member of the 0331 cracked club.
And already have a 7120 at the machine shop.

Can anyone who did this swap on their 2000 or 2001
verify that the exhaust manifold needs to be changed
to an earlier manifold design? If so why? Any pics?

Thanks
Eddie
 
eddieeddieg said:
I had just become a member of the 0331 cracked club.
And already have a 7120 at the machine shop.

Can anyone who did this swap on their 2000 or 2001
verify that the exhaust manifold needs to be changed
to an earlier manifold design? If so why? Any pics?

Thanks
Eddie
Eddie, while you can use the current exhaust manifold, you'd be money ahead by replacing it with an aftermarket (whatever you pocket can handle). The durn things have a habit of cracking as well and if you go through all that work to swap the head and remount everything, you'll just kick yourself in the arse if if goes 6 months later.

I guess I was lucky (or not) but my exhaust header had cracked in '03 and I replaced it with a Banks.

For what it's worth, ALL exhaust manifolds with fit the head, but not all exhaust manifolds will fit your exhaust system.
 
I've also got the "0331" head on my 00'(it does have the cast manifold also) and so far no problems(90k). My radiator blew out the other day, I put in a all metal 3 row, new t-stat and pump, as well as a tranny cooler. Hopefully with some maintanance I can keep it from cracking until its time for a new motor.
 
The peak time for 0331 heads cracking is between 60k and 90k miles, but I've heard of one head cracking at only 13k miles and another at 120k so there's no way of predicting when it'll happen and if it'll happen. There's also no mileage when you can consider the head "safe" from cracking. It's all down to the luck of the draw.
 
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