1990 XJ 4.0 swap - compatibility, goodies, etc.

[JeepFan3]

My 1990 XJ's engine has lost compression on #6 (30psi) and my oil pressure isn't what it should be, so it's time for a rebuild. I'm looking for a donor engine so I can still drive my XJ if necessary while I build the new motor.

From what I have found on this forum, any XJ or ZJ engine through 1999 will work with my Renix as long as I retain my flex plate, intake/exhaust manifold, distributor, etc. Is this right?

Since I will be doing the rebuild myself, is there anything I should do (or shouldn't do) while I am at it?

I am considering boring it, aluminum pistons, bumping up the compression, cam, etc. Nothing too radical - just want a little more oomph. This vehicle is basically my daily driver with very little off-road activity. Any suggestions or advice would be appreciated. Thanks!

 

[cruiser54]

My 1990 XJ's engine has lost compression on #6 (30psi) and my oil pressure isn't what it should be, so it's time for a rebuild. I'm looking for a donor engine so I can still drive my XJ if necessary while I build the new motor.

From what I have found on this forum, any XJ or ZJ engine through 1999 will work with my Renix as long as I retain my flex plate, intake/exhaust manifold, distributor, etc. Is this right?

Since I will be doing the rebuild myself, is there anything I should do (or shouldn't do) while I am at it?

I am considering boring it, aluminum pistons, bumping up the compression, cam, etc. Nothing too radical - just want a little more oomph. This vehicle is basically my daily driver with very little off-road activity. Any suggestions or advice would be appreciated. Thanks!

This might help:

Cruiser’s HO into Renix Swap

This swap is easier than some will lead you to believe, generally those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.

The HO and Renix have some differences but none that can’t be overcome very easily.

Any HO engine from an XJ or ZJ through 1999 can be used. One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from the HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head for the sender.

You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use the Renix gasket. Exhaust ports are identical.
You will need to use your Renix distributor as it is different than the HO because they use different fuel management systems. The flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.

The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16” square drive or a modified 3/8” drive that has been ground down to fit. Do this before installing the engine.

As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.


Revised 03/28/13

 

[JeepFan3]

Awesome! Thanks for all the great info!