4cyl. to 6cyl. swap in an MJ

natep1 · Sep 20, 2005

Thinking about a new winter project and I stumbled across a nice deal on a 2wd 1990 MJ w/a blown 4 pooper.
What I wanted to know are what chassis modifications are needed to bolt in 4.0 block?
All I can think of would be the motor mounts & a tranny crossmember (putting in a 904).
Anything else that would need to be done just to get the block to fit?Thanks for any advice.
Nathan
(No luck on the search)

5-90 · Sep 20, 2005

The 90 MJ shouldn't have a lot of trouble taking the 4.0 block - if you were trying to do this with an 86, you'd be in trouble!

You'll want the engine, transmission, and (maybe) the transmission crossmember - I'm not sure if they're the same. Have you done any searching around here? I'm pretty sure this has been covered before. It sounds familiar, anyhow...

5-90

natep1 · Sep 20, 2005

I didn't have any luck finding the chassis info when I searched, maybe I used the wrong terms (who knows?).

I pretty much have everything (besides odds & ends) that I would need to do the swap.
2k based (soon to be) 4.7 stroker, all accesories & electronics for the engine, complete 2k XJ wiring harness, computer & radiator. All I need on the electrical end is a gauge cluster.
I will be using a fresh 904 (5-6k) because I already have it, it can be built up very easily and without too much expense. I may switch to an AW4 in the future but no immeadiate plans.

Fabrication wise, I am hoping it will be as "simple" as installing 4.0 mounts and making a crossmember.
Thanks for the info.
Nathan

Highlander · Sep 20, 2005

I'm doing something remotely similar, We are changing a 4 cyl 2wd to a 4.0 4wd.

It's an 87 do you think a 4l will fit in it? I've searched too but didn't see anything on it.

5-90 · Sep 20, 2005

Yes. The front clip for the XJ/MJ was redsigned for the 1987 MY to accommodate the long inline six block.

If you were working with 84-86XJ or 86MJ, you'd have to do a LOT of work to the front clip. However, most of the work is now done for you.

Don't forget to get all the donor stuff when you get the engine - electronics, wiring, and stuff like that. It will save you trouble. I'd also try to grab exhaust at least back to the catalytic converter - even if it's useless, you can still use it for a pattern.

5-90

Eagle · Sep 20, 2005

Direct swap if the chassis is '87 or newer. The 4.0L uses different motor mounts, but they go to the same place on the chassis. The crossmember is also the same, but you'll need the correct tranny mount for the 4.0L tranny you'll be using.

The 4.0L is a heavier engine, so if you're going to be running at stock height you should use springs from a 4.0L XJ or MJ. If you're lifting, you'll be changing the coils anyway so that'll be a non-issue.

CheapXJ did this swap a couple of years ago. He worked like an unemployed Frito bandito and got the entire swap done in something like 72 hours. I thought he had a write-up on it, but I've been mistaken before.

Pete M · Sep 20, 2005

It brings a tear to my eye when I hear of an MJ being given a new lease on life.

Jeep on!
--Pete

ComancheClub.com

Eagle · Sep 20, 2005

Pete M said:
It brings a tear to my eye when I hear of an MJ being given a new lease on life.
Jeep on!
--Pete

ComancheClub.com

I wish you lived closer to Connecticut. I need someone to help convince my wife that these MJs I have here aren't "basura" (Spanish for "trash").

rockwerks · Sep 20, 2005

good to see another MJ come back from the dead. The 904 for the stock 4 cyl will not bolt up to the 4.0 if that is your intention, you sill need an aw4 to hook it all up

Pete M · Sep 22, 2005

Eagle said:
I wish you lived closer to Connecticut. I need someone to help convince my wife that these MJs I have here aren't "basura" (Spanish for "trash").

If I had property and a little bit of money, I'd have quite a collection too. Heck, I'd probably work-over the junkyard to get my hands on the decent bodies that come through. I don't know the specific conditions of yours, are they sitting in the weeds, on blocks, pavement or what? Maybe if they were all in a neat row and looked like a museum collection?

Jeep on!
--Pete

ComancheClub.com

rockwerks · Sep 22, 2005

Pete M said:
If I had property and a little bit of money, I'd have quite a collection too. Heck, I'd probably work-over the junkyard to get my hands on the decent bodies that come through. I don't know the specific conditions of yours, are they sitting in the weeds, on blocks, pavement or what? Maybe if they were all in a neat row and looked like a museum collection?
Jeep on!
--Pete

ComancheClub.com

Im down to 2 MJ's and 4 XJ's in the yard.....Im doing good

natep1 · Sep 22, 2005

xjnation said:
The 904 for the stock 4 cyl will not bolt up to the 4.0 if that is your intention

I luckily have one from a 6cyl. Concord. It mocks up nicely.

4cyl. to 6cyl. swap in an MJ

natep1

NAXJA Forum User

5-90

NAXJA Forum User

natep1

NAXJA Forum User

Highlander

NAXJA Forum User

5-90

NAXJA Forum User

Eagle

Lifetime NAXJA Member

Pete M

NAXJA Forum User

Eagle

Lifetime NAXJA Member

rockwerks

NAXJA Forum User

Pete M

NAXJA Forum User

rockwerks

NAXJA Forum User

natep1

NAXJA Forum User

Similar threads