I just bought my first jeep, a 84 cherokee chief. It has the 2.5l 4 cylinder but i want to put in the straight six. Can I do this? I've heard that it wont fit in a 84.
Thanks.

OK, this question comes up a lot. Either for the 2.5, or the 2.8 liter engines. The issue is space. Your XJ is older, so the fire wall is closer to the header panel then the late models were. You will also need the CUs from the donor vehicles engine and trans, as well as the wiring harness to make it all work right. Can it be done, yes. Is it A TON of work, and not really worth it in the end, yes!! Your best bet is to obtain an XJ with the 4.0 in it already. There are a ton of them, and they can be had for really cheap!! This is my opinion on the matter, but you will have to decide if it's worth it to you or not!! HTH!!

Ok i have come across a 2.5L out of a 97 cherokee, will this work for me?

Yes but, same goes for the harness and CPU, and it's not a great motor. You would be better off with a GM 4.3 and a painless performance harness.

My jeeps engine is carburated and the one im buying is injected, can i put my engine parts onto the new engine to make it carburated? thanks.

Firewall is same distance on both- The radiator support is the difference, drill out spot welds and swap the 4.0 setup into yours! Yes it's a lot of work,and your way ahead of the game if you have a complete donor xj to remove all of the needed items.

So I would just need to put my radiator farther forward in the engine compartment? Thanks!

Your best bet is to buy a wrecked donor, then you will have every part that you will need. You will need to drill out the spot welds holding the radiator support ends in place, then swap in the 4.0 ends by either riveting them as i did, or use small bolts and nuts. Of course welding is always an option!