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)


82 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. I have an 88 comanche with 4.0 that I recently replaced with a 2004 grand cherokee 4.0. I had a guy that was doing the conversion of the wiring/replacing the pcm and harness. However he’s left me high and dry. Is there a harness than can be purchased that will do this?

  15. 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.

  16. 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

  17. 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?

  18. 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?

  19. I have a 1992 4.0 HO harness and computer out of an automatic. Will the harness plug into a 1987 XJ without any problems and I use the HO computer? I’m also putting it into a Manual Jeep (AX15). Is the automatic computer going to be an issue with the stick shift. I wanted to get away from the Renix since I plan on porting the head and doing a cam swap. Probably stroke it also

    1. Nope. Different animals.
      Stick with the Renix. The ECUs don’t care what trans you have. I have a stroker built and it’s all Renix. So do many others.

  20. Thanks for very good tips. I have a 87xj and a 95 zj engine that i will put in the xj, it has a 7120 head with the temp sender, so no need to relocate the temp sender right?

  21. Very useful site, thanks for putting it together. I have a ’90 XJ which is used mostly as a trail rig, but sees some road duty. Motor is tired. With the lift and tires, even after gearing down the diff I’m looking for more power. Time is scarce for me, so I’d like to source a stroker crate engine, many more options for 91+ non Renix crate motors. I live in CA and have to deal with CARB and smog. Since this swap appears to preserve the Renix ECU, intake and exhaust it seems that EGFR and all emissions are preserved and would be OK for smog compliance, correct? Also, is the Renix ECM up to managing these higher performance crate motors such that I’d be getting somewhere near the 270-300hp the builders advertise for plug-n-play with 91+ ECMs?

  22. Thank you. I would like to say this was my first jeep cherokee (xj) owned ever also I’m not completely a beginner but no master at mechanics neither followed this exactly had a few miss haps with parts being no good and a few sensors that i had to order but today its in started and running

  23. Hi Cruiser54 – thank you incredibly much for such a great list of tips and help! I am currently swapping in a 2000 XJ 4.0L and NV3550 5 spd + dash swap from the XJ into the MJ.

    All is working fine, but I’m stuck on the interior swap. I’ve already got the rear end working fine but now just the wiring itself for the dash swap. Do you have a detailed guide or any tips on the dash swap install?

    Thanks in advance!!

  24. I just finished this swap and now I’m getting a really rough idle its shaking the while car. I’m thinking I indexed the distributor wrong. Do you have any ideas.

  25. Thanks for this write-up!! My Q is not exactly about this swap but similar. I want to make it easier to change the CTS on my 89 XJ and so wanted to swap out the thermostat housing with a 92 housing that has the thread for a sensor. My Q is does the sensor for an 89 XJ fit this housing AND is this location ok for this sensor? I’ve been running rich and am certain it’s my CTS that needs replacing. Thanks!!

  26. Hey cruiser. First off thank you for all the great information you’ve provided on this site. I’ve managed to fix nearly every problem I’ve found in my 88 mj for almost no money thanks to your tips! I’m currently swapping in a motor from a 98 xj and have some questions about the coolant sensors: First, the plug in my 98 block for the temp sensor is in a different spot than on the 88. It’s closer to the rear instead of the front near the motor mount.. I’m assuming this shouldn’t make a difference but wanted to double check. Second, the temp sender I removed from the rear of the Renix Head is significantly smaller that the threaded hole in my thermostat housing from the 98.. am I using the wrong thermostat housing? Thanks again for all your help.

  27. I just put a 2000 block into my 90. Everything on the motor is 2000 aside from a 95 head and fuel rail. All Renix sensors moved over to new motor and tps adapted to HO tb. It started but ran rough initially. It will now idle decently but chokes with any throttle. I did swap the flexplate and got a new replacement from the parts store. I’m pretty damn sure the timing holes matched before installing. I followed you guidance on distributor indexing as well. Fuel pressure is good. I’m stumped at this point.

    1. Well, I swapped the old flexplate back in and it runs great! I did recheck that the hole match the original, it does. However, there is distortion from the stamping process. The distortion is obviously just enough to make the CPS get a poor Or erratic signal. There are not too many offerings out there but Pioneer FRA-333 and ATP Z205 are actually the same manufacturer and DO NOT WORK. If you have a cracked flexplate, only use an original one from the PnP or dealership. Pulling tranny twice sucks, but chasing your tail trouble shooting for endless hours just to pull the tranny a second time is worth the extra money a stealership asks.

  28. Cruiser, I swapped a 91 4.0 into my 89 xj didn’t have any problems during the swap I used my renix intake and exhaust manifolds and what not but upon starting I’m having a problem it won’t rev up above idle. I figured it might’ve been cause I didn’t have the CTS hooked up cause I didn’t want to remove that plug. Well I got the bright idea of just running the harness to the sensor in the t-stat housing. Well it popped two fusible links coming off the starter relay so I replaced the wires with a fused junction on both wires and it’s now popping the fuses. My question is could it be because the ecm is getting to inputs for the guage causing kinda like a mic feedback and that’s what’s popping the fuses and what could I do short of pulling that plug and using the original CTS. Sorry for such a long post but figured I’d try to give as much detail as possible. Preciate it.

  29. Hi Cruiser, I recently purchased an 88 Cherokee XJ 4.0 with the HO head (only) already swapped. For some reason, I keep getting a surging idle and stall issue in low gear. Any recommendations to solve this issue?

  30. Cruiser preciate the help with the renix to h.o. swap. Now I ran into a problem with a weird noise from the engine kinda has me worried. Can’t tell exactly what it is I went and checked my flex plate to torque converter bolts and manifold bolts, is there any way I could send you the video and see what you think. Preciate it.

  31. Cruiser, I just picked up a 88 with no engine mostly for the axles for my 87. After looking it over I’ve decided to put an engine in it. Problem is since there is no engine I can’t swap parts and I don’t have the sensors or the wiring harness. Is the harness I need the one that plugs into the c101 connector? Also, what’s the best way to find that harness? I think the other parts will be easy to find. Thanks.

  32. Hi cruiser, I have a 89 xj and every single con. Rod bearing spun at 300k she was still running pre teardown internal inspection would point to “she should be dead how is this still running)
    I want to go with a 94 h.o.
    What all do i need to make that work.
    Planning a trip to salvage next month(on nov.19.2023)

  33. Cruiser I changed my 96 xj motor with a 97 xj motor the temp sensor was wrong and I changed it but the head isn’t drilled for the sender would it be possible to change the 2 wire sensor for the 3 wire and just run the sender wire to the newer sensor plug

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