86 MJ swap options

[j_epcherokee]

i bought a winter beater with potential to be a trail rig when spring comes around. but the truck came with the little 2.5L and AX4. when i put my full-size axles and larger tires on it, i need more power. i have heard that to fit the 4.0 in the older body the firewall and core support need to be modified. id rather just swap some mounts and wiring harness. i guess i should have bought an 87 or newer, but a running driving jeep with new tires for 400 is hard to beat. let me know my options that dont require 1000s of dollars of modifications and as little fabrication as necessary. has anyone done a chevy or mopar swap? i want to stick to fuel injection if at all possible. let me hear your ideas....

 

[webbjeep]

I have an mj as well and I am considering swap the 2.5 to the 4.0 ...... heard its a direct swap. Not very direct for the 4.0 HO. As more wiring computers etc. need to be swapped. 4.0s are cheap, in my neck of the woods, they pop up on Craigslist for $80-$300 bucks.

 

[cruiser54]

Not much difference swapping in a Renix or HO. Which one to use is the least of the problems you'll encounter.

 

[XJ Beater]

the 4cyl 2.5 to 6cyl 4.0 swap is doable, its the 2.8 v6 to 4.0 i6 swap your thinking of where nothing lines up. the firewall is in the way, however alot of guys will use a gm 3.8 v6 out of a camaro coupled to the trans and transfercase from a 2.8 powered comanche/cherokee. gear it decent and you should be able to get by with the 4 banger for now

 

[yossarian19]

Look into the Chevy 4.3L v6 swap... I think Novak has some of the parts you'd need.
Its been done more than a couple of times for the reasons you are describing.
Otherwise... sky is the limit, really. Buick v6 would be cool if you can find one at the right price. LS / LT1 / Vortech V8 swaps are getting more and more common. I'd think the 4.3 v6 is your best bet, though, or maybe some other modern v6.

 

[Johnnie Walker]

Just throw a GM LS motor in it..

 

[j_epcherokee]

before i jump to v8 power, i would really just prefer building a decent 4.0/4.6 to put in. my biggest concern is the firewall and core support stuff. i am still somewhat confused. i know the 2.8 to 4.0 swap is difficult, but why would the firewall be different for the 2.5? is it because of motor mount location that there is more clearance or would it still be a problem because it is an 86?

 

[Gold Cobra]

Here's the best way to do it:

1. Sell, or part out your 2.5/2.8
2. Buy a 4.0 MJ

Bam! You're done! If you're smart about it, you could actually make money in that process. The swap is not worth the effort in my opinion when you can go buy an MJ with a 4.0 already in it.

 

[j_epcherokee]

Here's the best way to do it:

1. Sell, or part out your 2.5/2.8
2. Buy a 4.0 MJ

Bam! You're done! If you're smart about it, you could actually make money in that process. The swap is not worth the effort in my opinion when you can go buy an MJ with a 4.0 already in it.

very true.... i have very little in it, and with the amount of rust on it, i wouldnt be able to get much out of it. but, the cab itself is fine, the bed is going to get scrapped and the frame rails are fine. its a perfect shell to build a truggy. i just want some more power with as little modification as possible

 

[shelbyluvv]

If your truck is a late build 86 You might get lucky and have the firewall mods done already.

A 4.0 swap is just as much work as a V8 swap on a 86.

I am currently in the process of dropping a 5.2 LA Magnum out of a 94 ZJ in my 86 MJ. It is not a bolt in by any means. No one makes motor mounts for the swap.

The steering column out of the ZJ will not work without firewall mods.
The MJ heater/hvac system from the MJ with not work with out major wiring harness mods.
The ZJ heater/hvac system will not work without major firewall mods.
The MJ gauges will not work with the ZJ senders.
The ZJ cluster does not fit in the MJ dash without major mods.
The MJ fuel pump is not enough to feed a V8.
The ZJ fuel system will not bolt into a MJ with out some mods.
The ZJ engine, trans, and transfer will not fit without floor board mods.

As you can see it is a metric shit ton of work to make this swap possible. I am doing the dash and firewall mods first. It will then move onto dropping the the drive train in. I have a build thread going on Comanche Club of the project. I am currently stalled due to lack of funds and the holidays.

 

[j_epcherokee]

anyone know the build date when they did the firewall changeover? that would be awesome.

 

[FlexdXJ]

If your truck is a late build 86 You might get lucky and have the firewall mods done already.

A 4.0 swap is just as much work as a V8 swap on a 86.

I am currently in the process of dropping a 5.2 LA Magnum out of a 94 ZJ in my 86 MJ. It is not a bolt in by any means. No one makes motor mounts for the swap.

The steering column out of the ZJ will not work without firewall mods.
The MJ heater/hvac system from the MJ with not work with out major wiring harness mods.
The ZJ heater/hvac system will not work without major firewall mods.
The MJ gauges will not work with the ZJ senders.
The ZJ cluster does not fit in the MJ dash without major mods.
The MJ fuel pump is not enough to feed a V8.
The ZJ fuel system will not bolt into a MJ with out some mods.
The ZJ engine, trans, and transfer will not fit without floor board mods.

As you can see it is a metric shit ton of work to make this swap possible. I am doing the dash and firewall mods first. It will then move onto dropping the the drive train in. I have a build thread going on Comanche Club of the project. I am currently stalled due to lack of funds and the holidays.

Wow, glad to see someone doing one of these swaps instead of the ol "shove a 350 in there" routine. I will probably be helping on this one.......Thanks Russ for buying a bucket!

 

[austinaubinoe]

the 2.5L in my dads 2000 TJ puts out a decent amount of power, have you considered upgrading to a MPI 2.5L? Pretty sure its essentially the same block, so bolt in.

With the right gearing it could be a pretty decent crawler.

 

[FlexdXJ]

the 2.5L in my dads 2000 TJ puts out a decent amount of power, have you considered upgrading to a MPI 2.5L? Pretty sure its essentially the same block, so bolt in.

With the right gearing it could be a pretty decent crawler.

Around here, 4.0's are gonna be easier to find compared to a 2.5. Its an option I guess but may as well do the 4.0 swap.

 

[dasbulliwagen]

Everything Ive read about putting a 4.0 into an early 86 says that all you need is a little massaging in one spot that amounts to an extra 1/2" of clearance. And the core support shouldnt be a big deal.... just some minor welding, everything else is direct swap. Having a complete 4.0 donor will your best bet, youll have everything you need, and a good reference.

 

[austinaubinoe]

A 4.0 is NOT a direct swap......

I got to thinking, couldnt you just swap on a modern (well 10 years ago) MPI head and intake?