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swap '88 Renix to '96 HO- possible ????

stormy76

NAXJA Forum User
Location
CO
new guy here, I have a 1996 XJ- auto-4wd that motor went south on, & have found a 1988 XJ that I believe has a Renix motor w/129,000 miles on it- $500 for whole car. am wondering how difficult the "swap" would be ? I have good mechanical skills, but not so much in the electronics- i.e.-computers, sensors-etc. & what would be required to make it all function. I am 68 yrs. old & have not done a motor swap in 25 years, but is daughters car & has limited funds, so am doing what I can. tried search for swap info, found renix to 4.0 but no 4.0 to renix. any help would be appreciated. Thanks, stormy
 
Swap the long block and use the 1996 engine sensors and computer.

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

Remove and re-use as needed or required from the original 1996 engine: Fuel Injector rail, Intake/Exhaust manifolds, flex plate/flywheel, cylinder head, distributor-less ignition or distributor assembly, engine sensors, motor mounts, fan belt driven accessories and/or mounting brackets.
 
I have one question ? the Renix fuel injection has a fuel return line- the later fuel system does not !! what is done with the return line- just cap it off & leave it be, or put some kind of vent- like for a differential @ end of line ? I thought all F.I. systems had a return line to the tank, but my 1999 4.0 doesn't, so am confused. sorry, but am much more used to a carburetor- am pretty old school, but am willing to learn. thanks, stormy
 
Reusing the existing 96 intake and fuel rail makes it a non-issue. For the swap, you're literally going to disconnect everything from the old engine, pull it, and drop the new long block in. It's 50/50 whether you want to remove the intake and exhaust manifolds while it's still in the Jeep. I've done it both ways myself and find it less work to just unbolt them and push them aside instead of removing the exhaust pipe and fuel rails, etc. Swapping accessories over is easier once it's out though. No need to pull the transmission, just support it with a jack. Unbolt the flexplate and leave the t/c in the transmission, just make sure it's fully seated in the tranny before bolting up the bell housing again.



Find a good helper because you'll want a few extra hands at some point, especially trying to jockey the engine into position and line it up with the bellhousing. Even if it's just to hand you a beer. Take lots of pictures with your phone before you start undoing thing. It's really helpful when you try to remember whether that hose went over or under that wire, etc.
 
Thanks for the advice. Realized the stupidity of my last question after I posted it. My Daughter is helping me- been teaching her to wrench since she was 5, & she doesn't drink, which leaves more beer for me !! Have to take a few days off & let the body rest up - sucks getting old. Thanks again for the help & will post back on progress. Stormy
 
I am curious on the camshaft differences. I thought I read somewhere that the HO engine used a different camshaft.
 
And running a head with square ports and a intake with round ports

Huh?

Squarish intake ports and round exhaust ports on both these engines.

I can't find it now, but I had a photo of the Renix intake gasket over an HO gasket and there was a 3/16" difference in one spot on the intake ports.

FYI, I have done this swap both ways. It's easy.

I wrote the following to outline how simple it is to go from Renix to HO.

Up to 99 only!!

CRUISER'S MOSTLY RENIX TIPS
HO INTO RENIX SWAP
OCTOBER 31, 2015 SALAD 48 COMMENTS


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)
 
Hello New guy here too, was wondering how Stormy’s project turned out. I have a 96 xj with bad motor, my buddie gave me a banger deal on a 90xj engine rebuilt with only 2000 miles he got from a totaled 90 4.0 xj. Could I swap long block if I put all 96 stuff on Renix or would be best to use the 96 head. I see manifolds are different. I been told 96 computer won’t work with old manifold. I have a 96 manifold gasket and was gonna cut it so it matched 90 ports and slap her back together until a Jeep mechanic said it will run like dog poop(not exact word he used but close). I have 96 head at machine shop now being checked out and thought I would put it on Renix stick it together. Any info would be appreciated. Thanks Sagerat
 
Thank You Cruiser, that’s what I wanted to hear. Will I need to cut it to match Renix ports or leave stock. Also will flex plate need to be indexed. We have paint strip to match with torc converter. Thanks again, Sage
 
Use the 96 flexplate as the 88 has different slotting. The flexplate will only bolt on the crank in one orientation because one of the bolt holes in the crank is slightly offset. You don't need to index with the t/c. When pulling the engine, unbolt the t/c first and leave it in the trans. Give it several turns while pushing it to make sure it's fully seated before trying to bolt up again. Normally, when reinstalling the t/c, it drops in twice as it engages two sets of splines. There will be a little front-back play in the t/c after the bell housing is bolted up. If it's up hard against the flexplate and you can't turn it, it might not be fully engaged into the trans.


My best advice for something this involved is labeling everything as it comes off or gets unplugged. Put the screws into sandwich baggies attached to the parts as you set them aside. Take the cell phone and snap pictures/video as you go. It's incredibly helpful to be able to go back and see where things were connected and routed. Murphys law says you 'll wish you had them if you don't, and you won't need them if you do. :}
 
Just to let you guys know, we put the 90 4.0 in my 96. We had a start issue at first but I went to cruiser54 site and realized it was a ground problem. The 3 wires behind dipstick weren’t making contact. Had to cut the nob off by the harmonic balancer. It was interfering with the surpentine belt. The 96 had a different belt system. I took the elbow off oil filter and used 3614 filter as I keep them here for my Tacoma. Was a good deal the 96xj was given to me by my neighbor and I bought the Renix motor from a buddie for $100. One Time good deal we will use it here in the mountains for brush buggie. Thank you all for your help, I was told by another Jeep guy it would not work but thanks to this site works good Sagerat
 
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