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I know this has been hashed through the ringer here, but has anyone here actually attempted it? I know the radiator suport is different and suposedly the firewall! Does anyone on here have pictures, good ones, of the pre and post 4.0 engine bays? Or better yet, does anyone have there 4.0 out and a digital camera they can snap some pictures for me? I know "it cannot be done" Bull! I also know "its a lot of work"!!!! Lets just say I was offered a wrecked yj yesterday and am looking at my options! So can anyone help me here?
Do some searches on the old board. I have looked at several conversions, it is possible. The people who have done it say the firewall is no problem, needs one small dent put in it.
You will need the engine, trans, computer with harness, fuel tank, and a radiator support and front clip from a 87+ XJ.
I know that once on here or maybe jeeps unlimited there was a post that went to an writup that showed the whole process.
Most of the work lead me to belive that I would be ahead to sell my 2.5L rig and buy a 4.0L one, so thats what I did. Much happier. Only cost me $500 bucks to upgrade, would have spent much much more doing the conversion.
Ghost -- Although the reports mostly say the firewall is different, I have not been able to confirm that with engines in place. You just can't see well enough. I got flamed a long time ago by a guy who "knew" that was SPOBI and took me to task for warning people about it, even though Advance Adapters includes this warning on their web site and many other people have reported it. However, after claiming he would post pics to prove I was wrong, the flamer didn't post any pics.
There is no question, however, that all the substructure in front of the engine is different. Just park your XJ next to any '87 or newer and you can see what will need to be changed.
Here's what you're looking at. Earle from RI has an '86, and he wanted a 4.0L. He took his XJ to a small shop that specializes in Cherokees and asked them to convert it. After looking at it, they decided the easiest way to do it was to remove the windshield and doors from his XJ and from the donor, cut both vehicles in half through the A pillar and door sill/floor pan, and graft the new nose onto his '86 aft section. That's what they did and it came out well. However, if that's the easy way, spare me from ever considering the hard way.
So are you trying to tell me the radiator suport is closer in the 84-86 than in the 87 up? That does not make sence because the fenders are the same. Time to get Zig to come by!
It is closer and completely different. Also, the '86 doesn't have the cross bar that the 4.0L radiator is supported on.
Don't forget that when doing a 4.0L conversion you also have to swap out ALL the underhood electrics and plumbing, as well as change the gas tank. That's why it really makes sense to just sell the '86 and buy a newer one. However, when you think beyond "body work" to all the other work involved, you begin to realize that cutting two trucks in half and grafting the 4.0L nose to the '86 tail probably is the easiest way to do it, if you have to do it. That way ALL the wiring, dashboard, and everything stays in place. There's no rewiring involved except splicing the few wires that extend from the front of the truck to the rear. Replace the gas tank, hook up a new fuel line, and go.
Back in 1987 I had a 85 XJ with the V-6 and when the 87 4.0 came out there was no comparison - I sold the 85 and bought a 87 - ran it for 11 years!
Now a 4.0 87 - 89 can be bought for $1000 or so and it doesn't seem worth the effort to convert an earlier one. But if you have all the parts - not just the motor - but a complete donor with trans, d-shaftss, fuel tank & pump, lines etc and a lot of free time - have fun.
Been there, done it. Won't ever do it again. If you want a 4.0 that bad, sell it and buy a year that had the 4.0 in it. I doubt that it would have been easier to cut the car in half like that shop did. It just is not worth the effort, especially with the prices for the early 4.0 models.
Let's see, IIRC I cut the firewall out and replaced it with the firewall from the donor (about a 2' x 3' section - you have to go far down into the trans tunnel for everything to fit - the firewalls are VERY different), change front crossmember (that was fun to cut them out - NOT!), radiator core support had to be changed, which also required that I change the welded-in peices that support it (just behind the headlights) which also required reshaping at the front of the inner fenderwells, you lose the factory lower fender supports and have to get creative with those. I was working on a '86 body, and the donor was an '88. Had I not just spent a couple grand on bodywork and paint on the '86, I would have dumped it and got a '87-up to work on. I wouldn't even want to start trying to imagine what the wiring mess would be - I just pulled the entire harness (dash, interior, etc...) out of the 88 and put it into the 86 so I didn't have to get into that. You also need the motor mounts and track bar mount from the 4.0. Then there were the 100 or so other little things that needed massaging.
you could always drop in a 3.4 outta a fourth gen camaro or firebird, its strictly a bolt in deal, with the exception you need to get your current flywheel balanced to zero. check into it, i did cause i'm not willing to sell off my jeep just because it has a crappy powerplant. we're jeepers, if you dont like something, improve it!!! maybe i just dont find vehicles, especially ones we've spent time on and customized and made to suit our needs as disposable. maybe i'm wrong.... i dunno. anyways, sorry for the rant and check into that 3.4 swap.. its gotta be outta a rwd vehicle as transverse mounted ones are totally different... 3.1's are also a bolt in deal. good luck.
Second, I've seen it done, on a 1984-1985 XJ. No firewall modification. Relocation of the front items (radiator etc.) was done, but nothing at the rear of the engine bay. Admitedly, it was not an easy job.
Third, I am not sure where the originator of this thread lives, but in some countries other than USA, the local laws/market conditions, might not allow someone to get a newer truck.
I was planning to take that same route (4.0 lt HO transplant), when I learned last January that some stupid bureaucrat had brought out a law, that does not allow you to swap an engine in your car, which is over 250 cc from the original. So I guess all I can do is do a very recent 2.5 lt MPI transplant :-(
Yeah my vote would be to forget the 4.0 deal and throw in a 3.4 from a Camaro. That motor was designed basically as a bolt in replacement for the 2.8 and its HP is about the same as a non H.O 4.0 in stock form. And because highschool kids love camaro's I am sure that finding a cracked up one wouldn't be very hard.
Hey Ghost, I'm right with you. The guy I bought my donor motor and tranny transplanted a 4.0 and yes he had to splice in a new section of the firewall. When he tried to fit the 4.0 in it wouldn't fit so he had to pull the whole thing and start cutting and welding. Luckily he still had the donor vehicle to caniblize. Now he did swap engine, tranny and x-fer so that might make a difference. I can't see mating a 4.0 up to an AX-5. I would like to meet the person who swapped it without the modification 'cause he must have done some pounding with a big hammer. I'm looking for more power too and curse my 2.5 everytime I climb I-70 through the Rockies. No one loses me on the trail though!
One thing I did contemplate when I had my '85 was this:
Find an '88 or newer S-10 or S15 4X4. The V-6 versions will have:
4.3 L V-6, 700R4 automatic transmission, NP231 T-case w/driver's side drop
My plan was:
Dump the FI intake and get an Edlebrock 4.3 intake for a four barrel carb,coupled with an Edlebrock 500 CFM carb w/electric choke. Slap it in,get the driveshfts made up,and it would be a done deal.
In the real world (my wallet speaking to me):
As we can all attest to,it always looks good on paper. aperwork It's when you start actually DOING it,and shelling out the $$$ for it that it starts getting complicated. Go with another,4.0 powered,later model XJ. You will be much better off,and not in the long run,either. It will be an immediate thing! :thumbup:
Well my budie with the totaled yj offered his to me but has not given me a price yet. There is a couple of other options. I could get it and part it out and use the cash for a FI 2.5 or another friend knows of a 4.0 xj with a blown head gasket for 500 i think. I could get the 4.0 and drop the yj engine in it. Need to look at the cost of it all! The yj and the other xj that is. Then again, yet another friend got rearended this week in his 92 xj and offered ti to me for the cost of the salvage.......
Cam it and replace the stock carburetor with a "real" carburetor. Other wise just buy a decent '87+ XJ and transfer your mods. Why mess around with salvage jobs? There's a reason it's salvage -- it costs more to repair than the vehicle is worth.
True, I have a cam for my 4 popper and am thinking of a weber. I do however want to get into the xj salvage business though. I love these things and need a way to get extra cash for my addiction! LOL!
Second, I've seen it done, on a 1984-1985 XJ. No firewall modification. Relocation of the front items (radiator etc.) was done, but nothing at the rear of the engine bay. Admitedly, it was not an easy job.
Having done this swap, I can say that there is ABSOLUTELY NO WAY it can be done without firewall mods if you are using the stock motor mounting locations. By the time I was done, you could not see the modified firewall, so is it possible that you just didn't look close enough? IIRC, the recess in the firewall is like 5" or 6" deep. Though I didn't try it, I'll be money that there isn't enough room to move the engine far enough foreward to do it without firewall mods.
Well I went out and measured a couple of distances under the hood of a 99 xj. The 84 radiator suport is actually 1.5" further from the fire wall. I'll try to get a picture this afternoon that I can post tonight! However, I believe that the problem would come in lower on the firewall. down where the tranny and engine meet. It will probably not be done by me but I may have acess to a wrecked yj and xj. Still waiting to see what happens. Right now I am leaning towards cam and weber till i rebuild the 2.5! I think one thing that would help me is to regear. I do not think the 3.73 and 2.5 5 speed are going to get along well.
