1991 4.0 to replace a 2000 4.0

I know I should know this and I might but its been one of those days. I just picked up a 2000 XJ sport with 90k from a college girl that didn't understand why the Jeep drinks 2 gallons of coolant a week, but never drips anything.... here's the funny part its been doing it for 3 years! That's a lot of scratch for coolant . So it popped its head a few years ago and now its got a knock, go figure. So I picked it up for stupid cheap, or to put it into terms she could understand "25 gallons of coolant" . Anyway I was going to drop in a low mileage 4.0HO out of a 91 that got doinked last winter. I know I got to swap all the intake and harness from the 00 to the 91 block.... but is there anything else I'm forgetting? If I remember right the block should be the same.
-Chris

The short block for the 1991 will be a bit heavier, and will not have the main cap brace that is on the 2000 (but the brace can be moved - just take the hardware with it.)

The top half is what's different - and the 1991 top half should drop right onto the 2000 short block. You may need to change sensors (OBD-I to OBD-II - I don't have a list of what's changed and what's not generated yet...) but there shouldn't be any trouble with fitment.

I was thinking of using the whole 91 motor (block and head) but I planned to use the intake, sensors and bolt on's that were with the 2000. I can't and don't want to use the crap 99+ heads.
-C

BonesBrosChris said:

I was thinking of using the whole 91 motor (block and head) but I planned to use the intake, sensors and bolt on's that were with the 2000. I can't and don't want to use the crap 99+ heads.
-C

Click to expand...

You can, but you may have trouble getting the exhaust ports to line up between the manifold and the head (the ports on the #7120 head are larger than the #0331.)

If you have the ability to have a new downpipe bent, you can use the earlier manifold and head, and the later intake, I'm sure.