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4.0l WJ into a XJ


NAXJA Forum User
First off, no replies about a WJ will not work in a XJ. It gin will work, just takes a little work, which is why I am doing this thread.

The 4.0l in my 94 Cherokee throw a rod and made a nice window in the block. The engine was close to 600,000 miles with 200,000+ since last rebuild. Yes, It is the original engine. I knew I should have changed all the connecting rods during the last rebuild.

To answer why I would use a WJ engine, It was five miles away @ $250. Next closest engine was about 4 hours away @ $500+. The engine build date November 7, 2001. I would rather replace the mechanical fan with an electric one and use the accessories from the 2001 engine since there is a tensioner, but the A/C in my Cherokee works and do not want to rerun all the A/C lines.

The areas in yellow need to be drilled and tapped, the areas in red need to be material relief.




To get the engine mount brackets to fit properly, only the rear most boss on the driver's side needs to be cut back and drilled and tapped and a spacer installed on the front boss on the passenger side. These are the only problems I have found to get the engine to work in a XJ.
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 the 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)
OP agrees with you Cruiser.

He spells out the work he had to do to get the motor swapped in.

I also know that Evowheeler swapped in an 06 TJ block into his 99 XJ within the last year or so and had to do all the modifications that you note. He didnt realize the differences until he was in the middle of the swap and had already spent the money on the block. By that time, he decided to continue down the rabbit hole.
Bummer we can't see the pics.

PM sent to OP. I will host the pics if need be.
I started down the rabbit hole around 2004 or so. 3K engine for $800. I did do the motor mounts like the OP described. I did sell off the head. Bought the motor the head was installed on, with out the head for $40. Still, sitting in the '88 MJ.
There is a write up on Great Lakes XJ forum on what to do. The WJ's water pump has an extra bolt. Also, one of the holes in not in the same clocking. I think all the bosses are there to drill and tap. Brown Dog makes conversion motor mounts. I did plan on getting the correct head and run electric fans. Then I bought a stroker kit from Russ Pottenger.

I could take pictures of what I did, if you think that helps.
Is the WJ 4.0L any different in terms of combustion efficiency, e.g., improved port design, improved combustion chamber design, improved intake manifold design, improved exhaust manifold design?

Right side: https://photos.app.goo.gl/uzvgb18knp62ku8FA

Timing cover: https://photos.app.goo.gl/J2rb5JhbbQSDHyj1A

Water pump: https://photos.app.goo.gl/B7UPwyNBTbvscqM26

Left side, notice added boss for mounting the A/C compressor: https://photos.app.goo.gl/LCkJD1XBf9PUxUUw6

Right side engine mount: https://photos.app.goo.gl/PSCGFsaoMQQmV3rw8

Oil filter and oil sending unit: https://photos.app.goo.gl/BKjH3PPHQe37BxUm8

Left side boss needing to be trimmed ~ 12mm - 13mm: https://photos.app.goo.gl/HBPurY11nqpCXtoZ9

flat boss on head to drill for temp sensor: https://photos.app.goo.gl/NfzGLcMQ9uTWSR9S8

Keeping the early XJ valve cover, the stamped steel in garbage, IMO. Would love to use the coil pack ignition, but not going down the rabbit hole of multiple O2 sensors. https://photos.app.goo.gl/zwHsnAR4mevAGUWf6

Left side engine mount, using only the most accurate of measuring devices: https://photos.app.goo.gl/q2LQNUV2gkrFpNbq7

Old engine, metal fatigue is crazy. Should have replaced all the connecting rods on the last rebuild: https://photos.app.goo.gl/aYMbNZs5hoY4L5TB9

Cruiser54, I read your post about interchange between years on numerous Jeep forums, but still decided to tackle this chore since the closest XJ type engine was 3 hours away,$400 more dollars, and still a junkyard motor needing rebuilding. The closest machine shop was 1.5 hours away driving back roads. The besides filling in the unused bolt hole for the water pump, most of the problems are drilling out the bosses and trying not to break a drill bit in a blind hole.

I think I have all the relevant picture links.

94 Cherokee SE
97 Grand Cherokee Limited
08 Commander Limited
I'm not sure with all the work and mods/different parts you need that there is any cost saving?
I'm not sure with all the work and mods/different parts you need that there is any cost saving?

Except for not taking the timing cover off the XJ block, the price of WJ block was dirt cheap plus machine shop work and gaskets/ seals. My total is about $1500 USD. I would have preferred having a ZJ/XJ block, but living in rural America with only two salvage yards within 30 minute drive, pickings are slim. Seems no one is trashing older Jeeps. The closest major salvage yard, LKQ, is a 2 hour drive and they want blood for their engines. Foe me, the extra work is worth the time and money saved.
I don't know of any change, so if there is a difference please elaborate!

The rear main seal for 2000+ 4l do not have the locating ears of the earlier seals. the earlier seals can be used in the later main cap with the carful trimming with a razor blade. Ask how I know it can be done. :laugh::laugh::laugh:

87-99 seal https://drive.google.com/file/d/1Myek842ya6KPYfVLzcTqrkxhMzeupnKM/view?usp=sharing

00-06 seal:
Here's my reasons for using a WJ block: The first time I rebuilt a 4l engine in my first XJ (88), the "good" used engine someone sold me was so beat down, it might as well been a dead horse. To say the valve cover was clogged with sludge was an an understatement. The sludge had solidified into something akin to charcoal briquettes. When the machine shop was done, the bores finally rounded out at 60 over and the crank at 10 under.

When I pulled the valve cover on this WJ engine, it was clean like a new engine. Besides having to sleeve a cylinder because the piston exploded, the other cylinders only had a final bore of 20 over, crank just needed a light polish and remained standard size. After discussing things with the machine shop, a couple of experienced guys that probably started work back in the 50's or 60's, the engine had been rebuilt before, but the engine was not put together right, due to the piston exploding. Either the connecting rods were put in the wrong cylinders or the connecting rod was already bent during assembly. All the connecting rods had the numbers crossed out.. I had all the rods replaced with new pistons.

I could have driven 3 to 5 hours away and gotten a XJ specific motor, but would it have been worth the time and money to get a "good" engine sight unseen? Having seen what a beat down engine looks like and having seen many XJ's at the junkyard, I did not think it was worth the time and money to get the "right" engine.

When Cruiser said Chrysler did a clean sheet revision, I half expected all the bosses from the 4.2 and earlier 4l would have been removed. Everything is still there. If I wanted to stick a WJ motor in a CJ, all the bosses are present to mount CJ accessories, but would need an early 4l intake to mount everything.

At some point, rebuildable XJ blocks are going to become scarce and the only option will be either WJ blocks or cheaply made blocks from China. Go talk to some flat fender guys about their block selections. Really should have bought that CJ2A 20 years ago for $500, then I wouldn't be here having people tell me it is to much work to slip a WJ block in a XJ.

Rant over LOL
The water pump has the turbine impellor like the 'true' HESCO water pump. I believe its rotation is reverse of the XJ's.