0331 Head Cracked, Replaced with 0720 + Questions

Back in February I found a crack in my 0331 head the day it must have come to light... Regardless I scooped up a 0720 head cheap and then had it refinished for another 65 bucks. It was in great condition and such so I went on with my swap finishing it up right before surgery.

I have gone through the whole 0630 & 0720 head swap "Bible" and took everything and followed the information with exception of the exhaust manifold. I understand some people say that it WILL NOT seal properly but also through some of those same threads I read a few people who did get the 2 piece cast manifolds to work on a 0630/0720 head. I NEED to make my 2000 (2) piece manifolds to work I do not have any other choice.

I have a Cali Emissions bullshit set up with the 2 mini cat / pre cats and 4 oxygen sensors.

I DO NOT have a job any more as I was laid of 1 week after I returned from reconstructive surgery. I have 0 income thus it HAS to work

I DO NOT have any money to buy or fabricate or swap other parts on as my Jeep was T-boned by a box truck after only walking again for 15 days and only the 4th time driving the Jeep since putting on the head.

Those are all the reasons I have to make the 2000 headers work on a 0720 head.

I am aware that the ports are smaller by roughly 3/8". The 0720 ports are 3/8" larger in depth. I saw that there was an adaptor plate and all it looked like was the 0331 manifold gasket made into a sheet of aluminum so that it had something to seal against. If this is the case why couldn't I just use the 0331 gasket against the side of the block as it is just as smooth and structurally sound? I understand that the exiting exhaust gases will hit a headwall as it leaves possibly causing reversion and providing additional heat but seeing as the exhaust manifold ports have some thickness to them wouldnt that provide enough pressure against the head to seal them off simply using just the 0331 gasket & manifolds?

I understand most answers would consist of "aftermarket headers are larger ports and they would work" but I unfortunatly do not have that luxury as No Job = No funds. What little funds I had went into getting a new head as the Jeep was the only thing I could drive after surgery and then some clown blew a redlight at 50mph in a box truck and Pwn'd my Jeep. Luckly I was able to use a buddies winch to pull everything back and it runs & drives minus its fugly with a black hood & blue fender but other than that I got screwed there is no money to buy new parts and I need to make this happen.

To anyone who's post I read about not having a problem using the 0331 manifold on the 0630/0720 head PLEASE inform me how you did it or what gasket you used or anything that might help me out.

the only way to make the 0331 manifolds work would be to have an adapter made ... if you try to bolt up the stock manifold to the 0720 head you'll burn through the gasket in a few blocks. the ports in the 0720 head are too big to seal properly to the 0331 manifold and there will be large gaps. The 0720 are a large tall rectangle and the 0331 are a small circle ...
I have the 0720 head and used a '93 manifold off that with the '00 intake.
take the 0720 exhaust gasket, place the 0331 exhaust gasket over that and line up the bolt holes. That's your template ... there used to be a guy selling the adapter a few years back when mine went ... you could start there ... you might get lucky.

Either way you go ... it's gonna cost money to make it work. hate to bear the bad news. Try seeing if you can rape a stock one off a parts car, or from a wrecker for dirt cheap. But going this way you'll also have to sort out your O2 senser issues as well ... and being Cali emissions means you ned all those O2 sensors to work right.

Other easy option is get a header for 00+

Re: 0331 Head Cracked, bought another head + Questions

I have a crack in my 0331 head, and i bought an aftermarket head on craigslist but it has the 2686 casting numbers on it? I know the 2686 casting is for an 87-90 but it has the bolt holes (boses) for the coil pack? Its little more heavier too compared to the 0331 head, Im confused about it. The port holes are the same size as well compared to the 0331 head. If anyone can give me some info on this I would appreciate it. :helpme:

Re: 0331 Head Cracked, bought another head + Questions

REXJ01 said:

I have a crack in my 0331 head, and i bought another head on craigslist but it has the 2686 casting numbers on it? It has the bolt holes (boses) for the coil pack? Im confused about it. The port holes are the same size as well compared to the 0331 head. If anyone can give me some info on this I would appreciate it. :helpme:

Click to expand...

REX: Why don't you post pics of where the 0331 head cracked and the port side. Then post pics of the 2686 head with the port side and the coil rail boss side. You may need additional posts in order to be allowed to post pictures.

x2 on the pics

x3. I dont know of any RENIX head that has coil mounts. Are you sure the mounts you see arn't bolt holes? There is four threaded holes on that side of the head. The front two are 4.5 inchs apart, the rear two are 2.75 inchs apart.

I will post pics of it but like I said, it's got the 2686 casting number and I'm sure the holes on the side are for the coil pack! I have looked all over the Internet trying to find some information on it and haven't found a thing! Their are some other numbers stamped on it, and I've searched them as well and still came up with nothing! The only thing I can think of is that it is a universal head,if there is such a thing for the 4.0 jeep engine? It's just bugging the he'll out of me! The head is very clean, and true so all there is to do now is put it on and hope for the best!

Are you sure it has actual coil pack mounts? they will be at ~45 degree angles
Like so (only pic I could find)

I'm positive they are bolt holes for the coil pack! I wouldn't have bought it if they were not on there! I have another question for anyone that can help me on this? I also need an intake manifold, can I use an intake from a 4.0L jeep wrangler or a grand Cherokee? My XJ is a 2001, what is innerchangeable? Thankyou fellow members, I greatly appreciate the help

use your stock intake, the exhaust will be the issue.

I used my stock 2000 intake (same as '01) with my '93 7120 replacement head ... had to use the '93 exhaust though as the '00 ports were considrably smaller and left gaps when mated to the '93 head. so buy a header, a short braided flexpipe and scavenge an exhaust manifold to downpipe flange (just need the flange and about 3-4" of tube) from the wrecker. that should make it easier to get the exhaust sorted ... then you'll need the O2 bung welded in the correct location.

I can't use the original one because a piece of it broke off when I was taking it apart, and from the looks of it, it looked like it had been broke for a while and the bolt was just holding it in place! So I need to know which intake I can use? I would imagine the intake on the 4.0L jeep wrangler and grand Cherokee are the same as the intake on my 01 Cherokee? As long as I use an intake from 2000 on up?

Yeah should work ... but there may be bracket placement differences. Check it against the original first.

Some of the later wrangler 4.0L intakes have hose location and fitting differences.

I am new to this forum, but I have a 2001 (mfg date 10/00) Cherokee Sport 4.0 / 6 cyl with a 0331 head and 112K miles. I have all the symptoms explained by many such as loss of coolant for a couple years before any started showing up in the oil. I believe the progression of symptoms was from a combination of head gasket and a head crack by the valve side at different times. Low oil pressure at idle has been seen for several years indicating some bearing damage has probably occurred as well.



On another forum I read about someone using a block seal product to seal the head crack and after a year had not seen any problems yet. I am having my 0331 head milled flat even with a crack and I plan to attempt a crack seal fix. I invite anyone that has attempted this with success or failure to post their feedback. I will use the feedback to attempt to use something unique, possibly a high temp epoxy with the right properties applied under some pressure to penetrate the crack as deep as possible. I will share my result with all.

If this type of fix is successful, it may help solve the exhaust port issue from using alternate casting types. I look forward to any feedback pro or con. Thanks

There are no magic repair potions, the only fix is an uncracked head.

A TJ or WJ TUPY 0331 head solves all the problems at once, everything fits, and it is very highly crack resistant.