4.0 Renix block(88) vs 91-95

[laxplayermjd]

I have been trying to research this alot. I know the casting numbers are different from 88-90 and 91-95 . But to actually build a 91-95 and put it in my 88 cherokee. Are the blocks different? Somethin about egr, knock sensor or coolant sensor i believe ive read. Would it be best to just swap in a 88-90 block due to the renix setup. Thanks for the input.

[Muad'Dib]

I have been trying to research this alot. I know the casting numbers are different from 88-90 and 91-95 . But to actually build a 91-95 and put it in my 88 cherokee. Are the blocks different? Somethin about egr, knock sensor or coolant sensor i believe ive read. Would it be best to just swap in a 88-90 block due to the renix setup. Thanks for the input.

If you already have a renix block why not use it?

Now if you need to hunt down and find a renix block, then going with a 91-95 block will still work.

IIRC, the boss for the knock sensor is still there .. just is not used on the 91-95.

EGR has to do with the Intake and exhaust manifolds, not the block... Id get rid of it anyway... unless you have to pass a visual inspection (no smog in my area).

Coolant temperature sensor ... now thats a good question. I think that the boss is still there on the block .. it just has a plug in it (on the 91-95) but i could be wrong. I know on the RENIX there are three. One in the radiator for the Electric fan. One in the rear of the head for the gauge... and one in the block for the ECU. Now i thought in the 91-95 it was still the same .. but i could be wrong. It could be that its in the thermostat housing because i know at some point they moved it there.

[laxplayermjd]

Well i have the block in it. I just recently bought the cherokee. It was overheated, the guy said he replaced the head im assuming with a newer 91-95 because i think the manifold is different so there is no exhuast hooked up. It runs but has a coolant leak at the back of the engine somewhere. Havent had the change to look at it. Not sure if somethin is cracked or it may just be some freeze plugs or that he misinstalled the other head. So im not sure is the block is useable yet. Just trying to get some more info.

[Muad'Dib]

If your going to pull the engine out of it, and are considering building a stroker .. just use what you already have.

Whats the casting # of the head thats on it? What about the block casting #?
This will tell you (and us) what you really have under that hood and can familiarize yourself with it all better.

For all we know he replaced the head with a RENIX head, but bolted up a 91-95 exhaust manifold. Who really knows..

The casting #'s will help you there.

[Bodo]

How about motor mounts and other bolt ons. Looks like they'll all be the same over the late 80's up through 95. Is that accurate?

[Muad'Dib]

How about motor mounts and other bolt ons. Looks like they'll all be the same over the late 80's up through 95. Is that accurate?

For the most part yes they are going to be the same.

[tirod]

The Renix used a thermal fan switch in the radiator, its only an issue if you go different. 91 up used a temp sensor in the water neck, not a block problem. The gauge sender was later tied to the computer to control fan switching. There are aftermarket kits to do the same if you want, which simplifies installations of different blocks.

That leaves the Renix knock sensor, the boss is there to drill and tap at worse, or jb weld it . . .