Motor Swap

[dboisen]

I have an 88 Jeep Comanche with a 4 liter 6cyl engine. I am wondering if anybody knows how new of a Grand Cherokee motor can I put in it. Thanks!

[jimoshel]

Well now that just depends. You can take a engine that came out of a dealers show room this morning and swap it in, IF, you know what you're doing, got the time and experience and possibly some help. You will either have to down grade the later engine to Renix specs or upgrade your Jeeps wiring, electronics to the later specs. Also the necessary mechanical mods needed. Did I mention deep pockets? In my humble opinion the easiest way would be to stay with the 4.0 engine and down grade it to Renix specs.

[ohio comanche]

Why would you want to change the 4.0 ? I just put in a new Jasper remanufactured 4.0. Love this motor......

[nitroxsteve]

Is he talking about using a grand cherokee 4.0?

[dboisen]

yea

[87Warrior]

The WJ and TJ share the same motor mount design, which is different than an MJ/XJ. Not to mention, the WJ did not have a distributor.

 

I am not aware if a ZJ block will bolt into an MJ/XJ or not.

[jimoshel]

I never even thought about it. Just assumed a 4.0 block was a 4.0 block and although the accessories might be different the blocks were all the same. I have a '89MJ needs a engine. I have a '98 and a '01ZJ with a good engine. Somebody want to come swap them for me? Settle the problem of knowing. :brows:

[Eagle]

A ZJ 4.0L engine will bolt into an MJ just fine. BUT ...

 

The question is about using it in an '88 MJ. The '88 used the AMC/Renault Renix injection/ignition system. That went from 1987 through 1990. Chrysler introduced their own injection/ignition system in 1991, and that's the same system that was used when they introduced the ZJ in 1993. So, to use a ZJ engine as it sits, with the ZJ ignition and injection, will require significant rewiring.

 

If you use the ZJ engine as a short block, or even a long block, and swap over the electronics and injection controls from the old engine, then you can drop the engine into a Renix MJ.

[Eagle]

  On 7/28/2013 at 2:59 PM, Eagle said:

A ZJ 4.0L engine will bolt into an MJ just fine. BUT ...

 

The question is about using it in an '88 MJ. The '88 used the AMC/Renault Renix injection/ignition system. That went from 1987 through 1990. Chrysler introduced their own injection/ignition system in 1991, and that's the same system that was used when they introduced the ZJ in 1993. So, to use a ZJ engine as it sits, with the ZJ ignition and injection, will require significant rewiring.

 

If you use the ZJ engine as a short block, or even a long block, and swap over the electronics and injection controls from the old engine, then you can drop the engine into a Renix MJ.

Remember that the Renix system uses a different flywheel and CPS than the Chrysler system. The flywheel and CPS MUST match up with the vehicle's electronics.

[cruiser54]

Here's some clarification:

 

XJ Cherokee and ZJ Grand Cherokee 4.0L engine blocks interchange.

2000+ TJ Wrangler and WJ Grand Cherokee 4.0L engine blocks interchange.

XJ/ZJ blocks and 2000+ TJ/WJ blocks do not interchange without significant modifications. (1991 to 1995 YJ and 1997-1999 4.0L TJ Wrangler blocks will interchange in XJ/ZJ and visa-versa).

TJ/WJ 4.0L Engine blocks underwent clean sheet design changes effective in the 1999 WJ Grand and 2000 TJ Wrangler. These blocks are not interchangeable with XJ/ZJ engine blocks. The reason is motor mount bolt holes and belt driven accessory mounting bolt holes are in different locations, or not present at all, TJ/WJ vs. XJ/ZJ.

                XJ: "Regular" (not Grand) Cherokees 84-01
                ZJ: Grand Cherokee 93-98 (Gen1)
               WJ: Grand Cherokee 99-04 (Gen2)
                YJ: Wrangler 87-95 (Gen1)
                TJ: Wrangler 97-06 (Gen2)

 

 

[cruiser54]

And then a "how to":

 

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

 

[dboisen]

Thanks for the help!

[Comanchemodder]

Thanks for the flywheel swap info regarding placing an Chrysler CPS into Renix.  What about vise versa?  Will a Renix flywheel work with the Chrysler CPS and electronics?

[carnuck]

neither work with the other. The '89 MJ I parted had an HO plate with Renix sensor and it just misfired so the guy I got it from gave up on it.

[ftpiercecracker1]

Personal, first hand experience here. I have a 93 ZJ 4.0 in my 90 and the only problem i ran into was the pilot bearing. Neither work with the other. The ZJ was an auto and my MJ a manual. I ended up making the MJ bearing work. Bare/Bear? in mind that all Renix electronics were kept. I did keep the 7120 head and installed a squid design intake as well, but thats another story. 

[dboisen]

I am having the same issue with the pilot bearing. How did you make it work?

[ftpiercecracker1]

Bench Grinder.  :yes:  Just take off a little at a time, as evenly as possible, until you can hammer it in. It will take many tries until you get it right.

 

  I suppose the proper way would be to take it to a machinist, but i didnt have that luxury.

[jimoshel]

I have used a bench grinder to reduce the OD of a pilot bushing. I have also used a reamer to enlarge the ID. If there isn't a machine shop nearby or you just don't have the funds try a electrical repair shop. They have a small lathe they use to turn armatures with that will work on a pilot bushing. That's what I have and use now.