It seems that the 86 model of the MJ Comanche only came with a 2.8V6 engine. Now I tried searching and didn't come up with anything, but has anyone every been able to successfully drop a 4.0L into an 86 Comanche?

 

The AMC 150ci I4 was the standard engine, with the GM 173ci V6-60 being optional.

The front clip was redesigned internally to accommodate the longer block of the 242ci I6 for 1987, but it can also be made to fit inside the 1986 engine bay. Mostly, the firewall was massaged to clear the back end of the block.

If you pillage around online, you should be able to find details on the swap from people who have done it. Note that you're going to need to swap the engine/transmission assembly and probably the transfer case - since the bellhousing pattern differs significantly. You may end up having to relocate the transmission mount crossmember as well - I don't recall for certain.

 

I would rather have an automatic transmission anyway, so changing out the transmission was sort of an idea I already had in mind.

Ill try and see if I can find some links where people have done it. Thanks for the info.

 

If it were an XJ I'd tell you to jsut find a 4.0L one. But since it's an MJ that is a different story. I can understand ditching the 2.6L and all but have you considered a late modle 2.5L from a 91-95 jeep? You can also put the 3.4L out of the Camaro in the 2.6L place. I had an 84 before I knew anything about xj's so I have researched it and considered it and some things I opted for an easyer path. What are you final plans?

 

Hmm, that is an interesting idea. My friend has a 93 XJ that we just recently converted into a 4X4 and we also did some engine work on. He has a 4.0L6 that has plenty of power and seems to run really good. Since the 87+ models also came with this engine, I assumed that the engine bay was not changed from the 86 to the 87+ models of the Comanche. So what I thought about doing was dropping in a 4.0 into the 86.

Correct me if Im wrong, but was the engine bay changed from 86 to 87?

 

correct, also you can swap in the gm 4.3 wich is a great motor with large aftermarket support.

 

They are very different.

 

This guy did the same swap. but the author of the thread didn't post the rest of the progress after he ran into a motor mount problem. and the last post was a year ago.

but there's a reference to a successful swap by radioflyer in the thread.

 

Yep - with a few other advantages:

1) Advance Adapters makes a bolt-in mount cradle for the SBChevvy - that will also work with the V6-262, IIRC.

2) The "Baby 904" used with the V6-173 was a wimpy little three-speed slushbox. The V6-262, if coupled with an auto, was almost invariably coupled with the THM700R4/4L60. Not a bad auto, and it came with an overdrive as well. Just avoid 1987 and earlier THM700R4s, if you have to piece the upgrade together.

3) The 4WD V6-262 drivetrain (S10/S15, K10, and K10 Suburban) also came with the NP231C transfer case (usually,) which has a wider drive chain than the NP231J.

Of course, the cradle will also accept the SBChevvy V8 - and the V8-305 and V8-350 engines are easy to find in 4WD drivetrains. The V8-400 is a bit less easy, and I think the V8-366 will fit in the SBChevvy cradle (but don't hold me to it. Ask AA.)

All of those are available in the K10/K20/K30 pickup & Suburban, with a variety of transmissions. Preference for the 4L60 (they can be had with the THM350/THM400/3L80, but they're all three-speeds. They're also damned near bombproof,) but you can also get the 4L80 (essentially a THM400 with added overdrive,) and they'll all come with the NP231C or better.

I'd have to go through my notes to give you more information than this.

 

In the 86 the firewall, front radiator support, and even the tranny tunnel were different. I know the firewall has to be "massaged" with a sledge. The radiator support has to be completely changed to the more modern version. The 3.4L will bolt up to your transmission and bolt in your mounts IIRC. There is a company that will set up a computer and wire harness for you. It is pricey but will give you the 3.4 FI. IIRC it was widely used in the 94-96 camero's. Might be 95 as the last year. By the time you work out everything that needs swapping to put a 4.3 or 350 in there IMHO you would be better off money wise with the 3.4L. That is what I was going to do with my 84 till I found a 94 for $200. But like I said its an xj not an MJ. MJ's are a lot rarer then the 2 door xj.

 

Thanks guys for the extremely helpful information. I definitely learned quite a few things. For now, I'm going to focus on actually getting the truck... but now I have a plan B and even a plan C for when that happens.

Its nice to know that I have options, and most of them are good easy options.

 

The 3.1L and 3.4L (both V6-60, both direct swaps for the V6-173) are available in the F-body (2WD only) and S-series (2WD/4WD.) You can grab the electronics and drivetrain out of the S-series to save yourself some headache, and pick up FI (all while you're swapping to a notably superior engine!)

Again, the 3.1/3.4L usually came coupled with the THM700R4/4L60 and NP231C.

If you end up having to piece the thing together, the bellhousing pattern is the same as for the V6-173. However, there were two versions of the engine - FWD and RWD - in OEM applications. This is further complicated by the fact that all three V6-60 displacements also had a Goodwrench Service Replacement engine available - which had starter motor mounting pads on both sides of the block! So, if you're looking for a donor engine only, don't neglect the FWD platforms. Slide under and look - if you have a starter motor mounting pad on the back side of the engine (as mounted,) you have a GSR block and it can be dropped into a FWD or RWD with equal ease.

 

just to stir up the pot some more... 6.2 diesel... share the same motor mounts as the 350... T400 tranny bolts right up and has the 32 spline output which is great for th 241 from a 88+ IFS chevy... cause its drivers side drop... has a whole 3 wires to worry about and needs no computer... but dont steal my idea yet... this is my build... lol... i want a MJ... im looking now... and if it goes as well as i think in the XJ... im doing the same with a MJ... lol

 

Isn't the 379ci the IHC/DuraMax Diesel? And it shares mounts with the SBChevvy? Is the bellhousing the same, or did it get a modified THM400?

I prefer Cummins Diesels, and my "pet project" would be a punched and stroked 426ci Hemi into an XJ (or play around with an AMC 401...) but I'd like to hear about this one if you can pull it off!

 

ive got acouple 6.2's im watching now... the 6.2 shares the same bellhousing pattern as the SBC's... so can run the 700r4's 4l80s whatever you want... just have to use the diesel torque converter... theres the alt wires, starter wires, and 3 others on top and thats it... no other wiring... the 3 are glow plug warm up, one goes to the temp sensor to work the "choke" setup... and i forget what the other one is... think just a power but dont remember what for... otherwise its all mechanical... in 88 they changed to the serpentine setup... good and bad... good is its one belt and gets rid of the problem with the V belt setup... over tightning of the V belt setup on the crank offsets the weight and makes for a nice busted crank... bad is its one belt... it snaps or AC goes out and your stranded... V belt system has 3 belts turning the water pump... so your golden... i think as long as you know not to over tighten the V belts and just deal with changing them once a year (which is a pain) then your better off... also the 6.5 turbo and exhaust will bolt right on with few mods to keep it oiled... but not sure if this will fit in a cherokee... guys in blazers and K20's get an average of what ive read around 22mpg... everyone says they are slow... but they are just as slow pulling a 50 foot trailer... so to me thats prefect for wheelin... im not looking to drag race the cherokee... thats what my 03 cummins is for... which im now selling to afford this project... lol... yes i want to do this that bad... cause i know it can work and i think many people will follow if i do it... also as for the tranny crossmember... i gotta build one anyways for the longarm setup... so ill just build it for the th400... ive got a 6.2 from a hummer at the local army surplus with a th400 bolted up to it... 13k original miles... hes asking $1500 for both... i think i can talk him down... but this makes this swap cheap and easy... also read several times the military version of the 6.2 (out of military vehicles m1008, m1009, H1) is better then the civi version... cant figure out how or why yet though...