Some of you have been following my posts chronicling the build of my daughter’s XJ “FrankenJeep II”. It’s come along great, it’s just about complete, and she’ll be taking off with it in a couple weeks. Building this with her has been a blast, and I don’t want it to end, so I’m seriously considering building an XJ of my own. I’m already scouring Craigslist looking for the right base to start from. I know exactly what I want; a 2-door, stickshift with 4.0. I’d like it to be 1992 or older so I have total freedom to mess with the engine without having to worry about emissions (25 years old is the cutoff in WA). I’m mainly looking for solid and rust free, I figure I’ll be swapping out much of the mechanicals anyway so I’m looking for a cheap project car, don’t even care if it doesn’t run.

So this brings up questions on “swapping out much of the mechanicals”:

- What are the best years for the 4.0 engine? I hear bad things about the early RENIX engines, and bad things about the later 2001+ engines. And I definitely want FI, not carbureted.

- If I find an early 80’s XJ and want to swap in a later 4.0, is that do-able? Or are there chassis/mount differences that turn this into major surgery?

- What about swapping a 4.0 into an XJ that has the 4-banger originally?

Thanks. As this project progresses, I’m sure I’ll have similar questions about best years and swappability of trannies, TCs etc., but for now let’s look at year/chassis/engine combos.

 

I'm sure people with more experience will chime in here, but:
Nothing wrong with the Renix engines, in fact, you might like them even more if you don't mind using a multimeter (just about everything on the engine can be tested fairly straightforward with a DMM); however, one major weak point in the 87-early 89' model years was the Peugeot BA 10/5 transmission, you can google pictures of em to make sure you don't end up with one of those, they're just bad news. Also, the cooling system can be a bit finicky, but its easy to keep up with maintenance or swap to the newer open system.

Swapping from the V6 or 2.5 engine is very very likely not worth the hassle, I would only consider it if you found a body that was absolutely perfect. Harnesses, engine mounts, nothing is quick n' dirty in terms of engine swaps. Swapping from auto to manual is pretty simple, especially for the older years. All the 4.0's are fuel injected, so no worries on that front.

 

its the 00-01 Jeep Cherokees xj with the bad head.
Cruiser always says this and I agree. So don't over look a Renix.

HO is better then Renix myth buster


Renix in 90 made 182 HP. HO in 91 made 190 HP. That's 8 HP difference.

HO only made more HP than Renix at higher RPMs and not a bit more torque. HO had a 58 mm throttle body versus a 52 mm throttle body on a Renix. That’s 20% more air available through the HO throttle body. The HO also had a better design header. See where I'm going with this?

It’s only a 4% horsepower increase…..

The whole 8HP was not mostly from the head, but from the bigger TB and better exhaust manifold.

Put a 60mm TB from www.strokedjeep.com on your present manifold using the Renix head, eliminate the "crush" in your headpipe with proper re-routing, and go for it.

HO stands for Highly Overrated.

 

Have you considered a Florida, Texas, or Arizona vehicle? Usually rust- free if you dont mind making a road trip .

 

Thanks all. Couple things I'm taking away from the above, please correct me if I have any of this wrong:

Don't fear the RENIX 4.0.

Fear the 00-01 heads

Don't consider swapping a 4.0 into a 2.5 XJ

Swapping from auto to manual no big deal if I have the right parts

Turning a 2WD into a 4WD is very doable (got that from other posts)

Most important thing: straight and rust free.

Let the shopping begin!

 

Wristwister, did I hear you correctly? In Washington 25+ years are exempt from emissions? I live in an emissions free county, but that sparks some questions for some of the issues for my jeep

 

Excellent summary!!

 

Good question Cyber, I assumed the 25 year thing was state wide, but maybe that varies by county? I know it applies to King and Snohomish counties.

 

I did some research and it appears to be state wide. Thanks for bringing it to my attention, I didn't have any clue on it!

 

So here's an interesting twist on the "build my own XJ" thing. Yesterday was my birthday, and as my present my daughter handed over the keys to her old XJ. Now we've picked that poor thing pretty clean of it's good parts in putting together her new XJ, but there's still a lot of good donor parts there: stick shift & clutch linkage, axles, various other parts. It's got the 2.5, so probably nothing I'd want engine-tranny-TC wise. We were originally just going to take it to the local 4X4 boneyard for scrap value, but now I'll probably hang onto it for a while for some more parts picking before dragging it to the grave.

 

If it has the 2.5 then I think it may have 4.10 gears. The rear is probably a dana 35 but you could swap the front axle into another 4.0 jeep then you would only have to regear the rear to have 4.10s.