HO into Renix Swap


This swap is easier than some will lead you to believe. And generally Pooh-poohed by 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.

  • XJ Cherokee and ZJ Grand Cherokee 4.0L engine blocks interchange.
  • 2000+ TJ Wrangler and WJ Grand Cherokee 4.0L engine blocks interchange.
  • YJ and 1997-1999 4.0L TJ blocks will interchange in XJ/ZJ
  • XJ/ZJ blocks, and the 2000+ TJ/WJ blocks do not interchange without significant modifications.

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.

Now that we know which engines we can use, let’s get down to business.

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

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 an HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head at the rear 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 a new Renix gasket. Exhaust ports are identical.

An alternative on exhaust manifolds:

As far as exhaust, you can use the Renix exhaust manifold and be fine.
If you want to use the HO exhaust manifold, you must go with an HO headpipe and screw your O2 sensor into that headpipe. Standard Renix harness is plenty long to do so.
A bung can be welded into the HO manifold to accept the EGR tube.

You will need to use your Renix distributor as it is different than the HO design. See Tips #12 – Setting Your 4.0 to #1 TDC and #13 – Distributor Indexing to be sure you get the distributor installed correctly.

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.


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)


43 thoughts on “HO into Renix Swap”

  1. hello sir. I am building a mj and i have all the wiring from the 99 donor for dash swap and front end swap. I have the enitire wiring harness actually. My problem is trying to do this while keeping the renix long block in it with aw4. I can get a ho head and intake and put on my renix block if that will work. Not trying to put in a Ho engine and trans because im going 5.3 t 400 in future. Ive read alot of threads and seems like your the man to talk to. Let me know what u think is the best way to go about this. thanks

  2. Hey there! I’m doing the swap right now but noticed my belt doesn’t fit? Is there a different belt I should be using?

  3. Not sure where to ask this Cruiser, so I’ll place it here. I reused the Renix A/C bracket when I swapped a ’98 4.0 into my son’s ’90 XJ. It has the pressed-in fan pulley. The bearing has failed. How do you change it? For now I have rerouted the belt, removed the mechanical fan and gone electric (dual aftermarket fans). But I have an overheating problem. Thinking new radiator and hoses next. Appreciate any help.


  4. North Florida. The junkyards around here don’t have much in the way of old jeep parts. With all the reading I’ve done I wanted to go with electric fans, but ended up disappointed! AFAIK, the radiator is original.

  5. Hmm… I’ll check that out. That would be a quick solution. If I can find the bearing I have a press as well. Thanks again, Cruiser

  6. Hi Cruiser. Not having luck finding the bearing. Headed to Miller Bearing (Motion Industries) to see if they can help me out. I think ID and OD of the bearing will be common, but the bearing is maybe 3″ long. Once this is resolved I will throw up some pics on my forum thread. Stay tuned.

  7. Here is what I found out in the world. Miller Bearing says they can’t get bearings for this application! Surprised the crap out of me. Says the bracket/pulley/bearing combo is OEM these days. Can’t imagine what Jeep would charge for this?? As if…

    Shaft is 5/8 diameter and the bearing is 30mm OD. MB says the entire shaft would have to be changed to 17mm for them to provide a 30mm bearing. Will check out Comanche forum.

    1. Cruiser, would you post the link again? I can’t see it, and I’m not finding anything relevant on the Comanche forum. Thanks.

  8. I just started a thread in the XJ/MJ non-technical forum. Thread heading is “Renix fan hub…..”. Hope this will help someone.

  9. Cruiser: thanks for providing info regarding my engine swap. Refreshing your memory, I but the 4.0 engine on my ’95 Cherokee stick and have 4.0 in a ’87 comanche automatic. After having read you send, there are several concerns that that are still a ‘gray area’ for me. If you so desire, you can communicate with me via email:
    bruskidave@gmail.com or just depress the dee-leete key to all this time consuming nonsense. The CPI from my ’87 comanche automatic is a concern as to how what is senses to the newer electronic. There are other concerns but at the moment, I’m becoming overwhelmed.
    David Bruski Sunday May 28th PM.

    1. Dave, sorry for the slow response. The site is supposed to notify me of comments. It’s hit and miss I guess….I never got notification.

      You have mail.

  10. cruiser, i just finished installing a H.O. head on my ’87 due to 4 cracks on the renix head. the newer H.O. head appears to be pre-’96 because it still have the temperature sender port in the rear of the head. my amateur question is what year spark plus should i be using? spark plugs from the original ’87 head or spark plugs between ’91 to ’95?

  11. Just did this and it will not run with out pinching return fuel line shut even with new regulator Any help would be great. Thanks

  12. Used the one that was in the 92 4.0 I took out, truck showed 233,000 and knocked on start. Friend had a 4.0 from a totalled 1988 with -55,000 mi.

  13. I’ve got a ’99 WJ. You mentioned the ’00 and up blocks wouldn’t work in an MJ/XJ but it seems the ’99 WJ fell through the cracks. Will my ’99 block replace my ’87?

    1. 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.

  14. Hello Cruiser, just curious if i have this correct. Would a 2000 xj block work with the renix head and accessories? I have an 89 Comanche, 99 xj (girlfriend’s, no issues), and a 2000 xj. The 2000 is toast as far as the body and such but runs great at about 190k. My comanche is almost 270k and has some coolant in oil, so im gonna do the head gasket. But i just got it not too long ago and can only assume it’s been ignored. It runs good as well, didn’t notice any coolant in oil until a week or two of driving it. So if i do the gasket i should be good awhile but who knows. Id like to do a swap at somepoint with the 2000 HO motor but retain the renix head if possible and use all the other necessary renix accessories with the HO thermostat, etc. Would that work? Also plan on concerting to the 2000 open cooling system probably at the same time as well.

  15. Great site cruiser, quick question on the distributor. Will the renix gear work with all 4.0s? I’m a ford guy and you have to match cam gears with distributor gears with them or they will eat each other. Thanks

  16. Hi cruiser I’m doing this swap now, and I can’t seem to locate the temp gauge sender on the back of my renix head. Would you happen to have a picture?

  17. Another question. What if I used a exhaust/intake gasket for a HO engine? Would it cause the engine to think theres a vacuum leak?

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