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What engine will mate to my XJ?

bigoltrux77

NAXJA Forum User
Location
Milwaukee, WI
Im getting tired of my 2.5L and would like a power change. I was wondering what other engine will bolt directly to my AX-5 transmission without any modifications? if this isnt possible, what mods need to be done and how hard is it. Ive heard that chevy 3.1L and 3.4L's will bolt up easily. Cann someone please tell me what goes into doing this type of swap? Im not very experienced when it comes to this type of upgrade. How do i modify my mounts so i can mount a different engine in my compartment? Cooling? Etc Etc... I dont want to do alot of cutting or bending etc. Thanks alot.
 
btt
 
i guess nobody knows anything...interesting
 
You gave a whopping 146 minutes for anybody to find the answers to multiple questions that are likely covered pretty well by searching; I know I've seen a few threads recently dealing with 2.5L--> Chevy swaps, including commentary on 2.8L Try using variations on those terms in your search.
 
Engine Compatability

There aren't a lot of engines you can swap into your XJ without getting expensive adapters. You are right that the GM 2.8 thru 3.4 engines bolt in however anything less than the 3.4 is a waste of you efforts as you will not get anymore torque or hp out of them than is available in your 2.5l. If you are going for the bigger series of engines such as the 4.0l Jeep or the 4.3 chevy then find a donor and get the whole drive train. The ax-5 won't stand up to the torque of a 4.0 or 4.3 anyway. I have an '85 2.5l like yours and decided to just go with what I have and get as many ponies out of it as I could. I have a 2.8l also but I'm transplanting the whole drivetrain from a 4.0l (stroked) into it. Not to be sarcastic but if you want more power then the best way overall is to sell your rig and buy one with a 4.0l.
 
Replacing the 2.5 with a 4.0 setup is not an easy thing to do, the firewalls are different as well as the radiators and about everything else. If anything you'll want to look at a 4.3/700 swap before considering that.
 
bigoltrux77 said:
i guess nobody knows anything...interesting

I suspect as soon as they saw "2.5L" most people lost interest. If you haven't already noticed, the 2.5L is the Rodney Dangerfield of XJ engines -- it doesn't get any respect (except maybe from HossHoffer).

Your question asked what will mate to your AX-5 tranny, so I'll skip the small-block Chevy and 4.3L GM transplants because they won't mate up -- and, as already noted, even with adapters they'll eat the AX-5 for breakfast.

The reason the GM 3.1L and 3.4L engines (rear wheel drive versions ONLY!) can be used is that they are the same small 60-degree block as the older GM 2.8L engine. Jeep bought the 2.8L engine from GM and used it in the XJ from 1984 through 1986.

Therefore, it makes an easy swap using factory (or junkyard) parts. You would need to get your grubby mitts on a set of 2.8L motor mounts and brackets, and you would need to get a set of XJ 2.8L exhaust manifolds (they are not the same as Chevy manifolds).

What else? You didn't state what year your 2.5L is. The Jeep 2.8L was carbureted and used a mechanical fuel pump mounted on the block. So did the '84 and '85 2.5L XJ. In 1986 the XJ 2.5L got throttle body injection and the fuel pump was changed to an electic unit mounted in the gas tank. In 1991 the 2.5L got multi-port injection, which requires a fuel pump that puts out more pressure than the throttle body pump.

Therefore, depending on whether you want to run the 3.4L with an XJ carburetor, aftermarket throttle body injection, or later model Jeep MPFI, you'll probably be faced with having to swap out the fuel pump.

Stryker is running a 3.1L in his MJ, but it replaced a blown 2.8L rather than a 2.5L.
 
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