Engine swap into 1989 Comanche Base

[CODriver]

Hello! I have recently purchased a 1989 Jeep Comanche. It has the 2.5 l4 with the AX-5 Transmission, RWD. I would like to have some more power to the car but also I  just want to have fun working on it. Would a 1991 XJ 4.0 l6 fit well in the car, and would it need a transmission swap?

Some photos from the seller:

Edited October 26, 2019 by CODriver
Forgot to add photos

[Pete M]

you will need pretty much an entire donor XJ.  

[CODriver]

Are there any simpler engine swaps?

Sorry if these questions are dumb. 

[Pete M]

well, lets start with the basics.  what size tires do you have now? 

[CODriver]

I’m not exactly sure, they are the stock tires from purchase. From what I know, almost everything is stock. ATM I’m out of town without my truck, so I can’t do any measurements

[Pete M]

those look pretty stock, so that rules out the weak feel of the engine as a result of big tires.  next up is to make sure the engine is running at its full potential.  new plugs, wires, fuel filter, check sensors, check injector performance, etc.  Plus I would run a compression check to make sure it's not just plain wore out.  oh, and I would double check the gear ratio in teh axle just to make sure it wasn't swapped out at some point.  it's super easy to do, just put the trans in neutral, jack up one of the rear tires, mark the driveshaft in some way and then spin the tire around exactly twice while counting the rotations of the shaft.  if it rotates 3 and a half times, then it's 3.55.  If it rotates a tick over 4 times, then it's 4.10s.  the 2.5L/5spd should have 4.10s but a lot can happen in 30 years so it's good to check.

 

the 2.5L is a great little engine.  It clearly isn't a powerhouse, but it's no complete wuss either.  plenty of guys are running them still.    If you want the 4.0 power, the XJ stuff is almost a bolt-in procedure, but you'll need most everything from an HO 4.0 XJ. 

[CODriver]

Thanks for the info! I’m having trouble getting over 55mph so it’s little worrisome. I do plan on changing those, but another big reason for the change is because I want a nice learning experience about how to change engines, and to do some hard work on the car before my grandfather can no longer help me.

[eaglescout526]

Define trouble. The 2.5L was made when 55mph was still the national speed limit. I can see 65-70 no problem. It really boils down to your shifting and how well the engine runs.

[Pete M]

if you can't get above 55, then something is definitely wrong. 

 

What about a 2-prong attack?  both fixing the truck, and then also buying a 2nd 2.5L engine and rebuild it for an eventual swap?  

[Wallace Krempa]

On 10/26/2019 at 7:15 PM, CODriver said:

 Would a 1991 XJ 4.0 l6 fit well in the car, and would it need a transmission swap?

 

 

 

That is what I personally did. It took me three months(about 3 hours a day) an 1 1/2 XJ to do mine. The 1/2 an XJ was for lift, axles and interior. They were both totaled but usable for what i needed to do. For both the XJ from the junk yard was $1200.