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0331 head swap question

dryad001

NAXJA Forum User
Location
Oak Creek, WI
I have a 2001 xj with about 115k on it and Im pretty sure the head is cracked. It is the 0331 head :(

I have an extra 1995 motor out of a XJ as well laying around, I dont know the head casting right now since its sitting at my shop but are the heads interchangeable?

Im sure this has been answered a thousand times but my searches came up empty.
 
The head will interchange but won't have the coil mounts(be creative). The bigger exhaust ports of the older head won't fit your newer smaller exhaust manifold ports though. Buy aftermarket headers or cough up the 4-500 for the new improved 0331 casting.
 
The head will interchange but won't have the coil mounts(be creative). The bigger exhaust ports of the older head won't fit your newer smaller exhaust manifold ports though. Buy aftermarket headers or cough up the 4-500 for the new improved 0331 casting.

The coil mounts are easy to make, hang them off the Valve Cover bolts. I made mine out of 1/8" aluminum flatbar from the hardware store with little more than a hacksaw and a hand drill.

If you have a spare motor use the exhaust manifold from that and the intake from the 2001. You'll just need to fab a downpipe from the '95's exhaust flange to wherever you decide to tie into the stock exhaust. I used a '93 head and used the older exhaust style instead of the '00 and had a new pipe fabbed-ish. If you go this route grab a couple long head bolts and chop the heads off to use as placement dowels to get things started (keep them as long as possible) makes life easier getting the cyl head lined up.

UNLESS, you have the dual pre-cats and all that goofty jazz ... then you need to drop down to the for sale section and talk to the guy there that adverts the adapters to re-use your exhaust with the older heads (think he sells the plate for $150-ish). The only other reasonable option would be to use a TUPY casting head from a newer 03+ TJ or replacement. You could also start swapping PCM's and all that jazz, but the means probably doesn't justify the end due to extra costs.

this guy > http://naxja.org/forum/showthread.php?t=919384 last post says he's still making them, that's really your easiest solution if you have the pre-cats and all the cali-like emissions doo-dads (4 x 02 sensors ... aka a BJ nightmare)
 
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Yup I have all the emmissions stuff on there. Pre-cats and all the stuff I didnt want...


I emailed the guy with the plate, just waiting to hear back.
 
Well I got the plate coming to me.

Got another wierd question. Im losing coolant, but the oil level does not go up. Im losing about a gallon every 2 weeks or so. Is it still possible that the head is not cracked??? I mean the engine has a ton of power, the oil pressure is around 25-35psi when hot and cruising and around 15-25 when idling.

This is my DD till spring so this has to last me at least another month or so. I was planning to lift sometime this year as well.
 
that points even more to a cracked head ... between the 3/4 cyl gap ... loosing it into the combution chanber most likley, and it's going out the exhaust pipe.
 
Ahh OK, Thanks for the help. Hopefully if the plate gets here this week I can do it over next weekend.

Im so happy I got another XJ.....lol. My 95 never had a problem and still miss it, although I see it everyday.
 
that points even more to a cracked head ... between the 3/4 cyl gap ... loosing it into the combution chanber most likley, and it's going out the exhaust pipe.


this is actually a good thing. if your 0331 head is gonna crack, best that it cracks this way. this means no coolant is getting in the oil which means no damage being done to the bearings.

i did the swap on my 01. my head actually wasnt cracked, blew a gasket. but i wasnt about to pull the head and put an 0331 back on again. i got a new one from clearwater, so far so good.
 
This is just my opinion: the adapter plate is a bottleneck, thus a non-ideal cheaper-way-out solution to making the older head work with the newer exhaust manifolds. I'd be interested if any of the aftermarket headers for the '00-06 4.0s have big enough ports to cover the older heads(http://www.naxja.org/forum/showthread.php?t=1078435). If any of you have these waiting to go on and an older head or exhaust manifold laying around, compare them(Please help the community out with possible solutions). Most people with cracked 0331s should just buy the new and improved thicker casting 0331s. 00' fed-emissions XJs don't have the pre-cats and thus can swap to the older style/aftermarket headers easily enough if they choose to go with an older head.
 
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The whole reason the adapter is needed, is because the manifold itself is smaller on the '00+ 4.0's ... If you place the newer manifolds against the older heads you can see past the manifold and into the heads exhaust port. The manifold on my '06 TJ looked like the same port size I had on my XJ when I did the swap ... Except the '06 had the whole precat arrangement.
So I ask you, how is the adapter plate a bottle neck, if the holes in the plate are slightly larger than the ones in the manifold itself ... It's the manifold that is the bottleneck in this equation.
If you can't ditch the newer manifold (due to emissions) this is the easiest solution, next to finding a newer cyl head. My 7120 head cost me $30 ... But then I didn't have to worry about precats so went with the 93 exhaust once I realized there was no feasible way to mate the old head to the new manifold (these plates were in the design phase back then).
 
I'd be interested if any of the aftermarket headers for the '00-06 4.0s have big enough ports to cover the older heads
I know the JBA headers have the larger exhaust port to cover the earlier heads.

The whole reason the adapter is needed, is because the manifold itself is smaller on the '00+ 4.0's ... If you place the newer manifolds against the older heads you can see past the manifold and into the heads exhaust port.
When I did the swap on my 2000, the stock manifolds weren't that small where you can see the head port from outside of the head. There was only like 1/8" of manifold to seal at the bottom of the port and a nice flat wall for the exhaust gasses to hit.
 
This is the way I see it.


The plate should be the same size as the exhaust port on the OEM manifold. This will create the same exact flow as the 0331 head. I will be using a 7120 head since thats what I have laying around (thank god Im a parts horder). The plate costs $110 shipped, and the head gasket, manifold gaskets, head bolts, VC gasket, etc costs $108 shipped via Rock Auto which is much cheaper than the big box stores around me.

If there was a feasible way to get around the precats (2-4 O2 sensors, not sure how many I have yet) Or I could use a 02 sim that takes the place of a sensor. The downpipe would be a problem unless I retro in all pre-98 exhaust which actully might work.


I wish I had more manifolds to play with, all I have is my current 2001 (split header) and a 1995 style long tube.


When I get time I can connect via laptop to the ECU to see if I can turn off the 02 cel light where the engine wouldnt go into limp mode. I would just need to see if anyone dissasembled the ECU code yet, if not I have a friend in AUS that is willing to help out.


The 02 sensors Im more concerned with are the front ones, I know I have 2 of them. These are the ones that dictate the STFT, LTFT trims during a WOT pull, or during regular cruising.


Now that Im rambling here, I wonder if I can just weld in a 2 02 bungs in the 95 manifold and just completely get rid of the precats??? The earliest I can do it this way since the XJ is my DD till spring/summer, but I can figure out where I need to stick the bungs before hand so its ready to go if I do decide to take the time to do it.


Here is the 02 sim I was talking about earlier:
http://www.ubertechnics.com/o2_simulator_2.5.aspx


Now Im almost positive that if I use the sim Ill throw a code for the rear 02 sensors saying some BS about being too rich/lean. The trick for that is to drill out a 1/2" spark plug anti-fouler so you can bring the rear 02s out of the exhaust stream...trust me this worked on my Evo for 50k miles.
 
Just show pics of the adapter plate so all can see how in the space of 1/8" (or whatever the thickness of the plate is) the 7120&0630 exhaust ports are necked down to the 0331. No discredit to the guy who's selling it, but it is not ideal.
 
Well if it wasnt for the adapter plate wouldnt the manifold be a bottleneck? I think what the person who is making these plates is so you wont burn through an exhaust gasket a few minutes after starting the engine up.

Im with you that its not the ideal way to do it but if it works, it works. It just has to last me a few months until I can really dig into it. The way I want to do it just might free up a few ponies as well and hopefully still work with the 2001 ECU without hacking any wires.
 
Actually the head ports are smaller than the exhaust ports, and thus a wall on the outside of the ports to prevent reversion. So if the adapter plate is an exact ramp from the earlier heads to the newer manifolds, that too is bad and eliminates the purposeful step.
 
You could replace the 00+ manifold with an earlier header and weld two O2 bungs in the appropriate place for the upstream sensors. Then sim out or modify the PCM to ignore the two down stream sensors. Of course that would be illegal.

Another option is to replace the PCM and associated wiring with an earlier one with only 2 sensors.

I have also heard of people grinding out the manifold ports, not using a gasket and instead use copper RTV on the exhaust, anaerobic sealant on the intake.
 
I have also heard of people grinding out the manifold ports, not using a gasket and instead use copper RTV on the exhaust, anaerobic sealant on the intake.


I was also thinking the same thing, seems like there a lot of meat on the manifold to do this... I guess we'll wait and see when I get everything apart to decide on what to do.

I'll end up starting another thread on how I did everything. More like a How-to post.
 
Heres the jist of whats going on.

The OEM 2 part manifold will be hard to port out to make the 7120 and 0630 heads fit correctly. The adapter is very much needed to make everything work correctly.

Im trying to source a 91-98 manifold to weld in the 4 02 sensors. Seeing my buddies ZJ in the shop Im more than convinced it can be done quite easily.
 
Finito!!!!

Seems like it runs good, oil pressure is a bit higher than it was so thats great. Ill end up doing 2 more oil changes every 500 miles to make sure that no water is left in there and everything stays clean.

Water temp is down a bit, Im guessing its due to all new fluid and t-stat. The coolant that came out just didn't look right IMO. It hovers right under the 210 mark.

One thing I did notice is that something is now clicking. It's coming from some solenoid on the passenger side firewall. Cant hear it inside so I guess its no biggie.


Anyways that the 7120 head can be replaced with the adapter plate. Not sure on the butt dyno since these things are dogs anyways. But the power seems to be right where it was with the 0331 head. Once I figure out how I can use an older exhaust manifold and keep the OEM ECM Im sure there will be a slight increase in power.
 
Seems like it runs good, oil pressure is a bit higher than it was so thats great.
What is it now at a hot idle?
Ill end up doing 2 more oil changes every 500 miles to make sure that no water is left in there and everything stays clean.
Good idea
It hovers right under the 210 mark.
Sounds good to me. Could just be the different t-stat
It's coming from some solenoid on the passenger side firewall.
100% normal. Maybe you didn't notice it before.
Once I figure out how I can use an older exhaust manifold and keep the OEM ECM Im sure there will be a slight increase in power.
See my previous post on the subject.
 
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