onlyinajeep726 Posted April 19, 2013 Share Posted April 19, 2013 I know, I know... this topic has been beat to death so much that a well trained mortician can't bring it back from ruins. Anyway... I'm not sure why so many people have told me that swapping in a 4.0 into my '86 MJ will require massaging the firewall with a BFH. The only problem I've seen is 4.0 radiator fitment and the hood latch is going to have to be changed. From everything else I can tell, the length front to back and side to side are near identical to that of my '88 XJ with a 4.0. So, what gives? Can someone shed some more light on this for me? Perhaps I'm missing something? My goal is to snag an HO engine and AX15 (external slave) and mate it to a Renix 4.0 wire harness and ECU. Will that work also, assuming fitment isn't an issue? Link to comment Share on other sites More sharing options...
Lee21490 Posted April 19, 2013 Share Posted April 19, 2013 I know, I know... this topic has been beat to death so much that a well trained mortician can't bring it back from ruins. Anyway... I'm not sure why so many people have told me that swapping in a 4.0 into my '86 MJ will require massaging the firewall with a BFH. The only problem I've seen is 4.0 radiator fitment and the hood latch is going to have to be changed. From everything else I can tell, the length front to back and side to side are near identical to that of my '88 XJ with a 4.0. So, what gives? Can someone shed some more light on this for me? Perhaps I'm missing something? My goal is to snag an HO engine and AX15 (external slave) and mate it to a Renix 4.0 wire harness and ECU. Will that work also, assuming fitment isn't an issue? Would love to help, But I bought my 86 with a 95 4.0 swapped into it already. /lazy Link to comment Share on other sites More sharing options...
mnkyboy Posted April 19, 2013 Share Posted April 19, 2013 I think it depends on the truck, some 86's had the cut out for the 4.0 and some didn't. Link to comment Share on other sites More sharing options...
Lee21490 Posted April 19, 2013 Share Posted April 19, 2013 I think it depends on the truck, some 86's had the cut out for the 4.0 and some didn't. I don't think so, I think it takes a little bit of tweaking to get it in. But i don't think its all that bad. The 4.0 wasnt even put in the comanche/xj till 87 Link to comment Share on other sites More sharing options...
mnkyboy Posted April 19, 2013 Share Posted April 19, 2013 I know that they didn't come out till 87 but the first 87s would have been built in 86 so the fire wall could have changed some time during 86. Could be why some have to modify the firewall and some don't. But then I have an 85 xj at the shop that had a 258 swapped into it that doesn't appear to have any mods to the firewall. Link to comment Share on other sites More sharing options...
zackcj7 Posted April 19, 2013 Share Posted April 19, 2013 I was looking at this with a friend of mine a couple weeks ago. We had my '86 parked next to a later model that came with a 4.0 and we couldn't find any differences in the firewalls. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted April 19, 2013 Author Share Posted April 19, 2013 I think I'm going to take a couple hours today and take a few different measurements on my XJ and MJ and get to the root of this predicament. If there's no appreciable difference, then my happy @$$ is going to be searching for a cheap wrecked '96 XJ with AX15. I just swapped in a 4.7 HO stroker into my XJ and did all the mods and adaptations to mate it to my Renix components. Fired up and runs like a champ, so I'm pretty confident I could do something similar to my MJ. Link to comment Share on other sites More sharing options...
mvusse Posted April 19, 2013 Share Posted April 19, 2013 Never witnessed it myself, but supposedly early 86 Comanches and Cherokees have a different firewall near the top middle. Link to comment Share on other sites More sharing options...
mpace6a Posted April 19, 2013 Share Posted April 19, 2013 http://comancheclub.com/topic/31039-big-swap-help/page-2 About halfway down the page shows the difference Link to comment Share on other sites More sharing options...
jbain Posted April 19, 2013 Share Posted April 19, 2013 My brother just finished stuffing a 4.0 into an 85 2 door..... he just too a couple measurements and since the dash was already out of the project and the donor he just cut out a section of the upper tunnel section with a cutoff wheel and welded into the project Jeep. A little grinding and some paint and it looked as good as the factory without the hammer. In all it took him about a days hard work but he felt it was worth it especially when it came time to replace the crank sensor. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted April 19, 2013 Author Share Posted April 19, 2013 http://comancheclub.com/topic/31039-big-swap-help/page-2 About halfway down the page shows the difference Thanks. I see that it is going to be a little more work than I figured. But, I won't let that deter me, minor set back. :hmm: I'd probably consider just selling the '86 in favor of an '87+, however, this thing is rust free and I've already put a lot of work making her look nice. Link to comment Share on other sites More sharing options...
mpace6a Posted April 20, 2013 Share Posted April 20, 2013 No problem. I'm just gonna go a step furthar and put a 5.2 in my 86. Similar amount of work that yields better results! Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted April 20, 2013 Author Share Posted April 20, 2013 I've seen two V8 swapped MJ's in my search for a Comanche. One was a 5.9L/360 Magnum swap from a '98 ZJ Limited and a '97+ interior swap. The other was a AMC 360. Both were nice and both were waaayyyy out of my price range ($6000+). Link to comment Share on other sites More sharing options...
mpace6a Posted April 21, 2013 Share Posted April 21, 2013 I've seen two V8 swapped MJ's in my search for a Comanche. One was a 5.9L/360 Magnum swap from a '98 ZJ Limited and a '97+ interior swap. The other was a AMC 360. Both were nice and both were waaayyyy out of my price range ($6000+). $6000 plus and your getting into cummins diesel swap price range. for that much i wanna know what all they did! Link to comment Share on other sites More sharing options...
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