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ZJ and WJ Grand Cherokees (1993 - 2004) Technical forum for the classic ZJ and WJ Grand Cherokees.

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  #1  
Old June 23rd, 2022, 02:41
NXJ NXJ is offline
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Will a 1998/99 WJ have the 0331 head?

Hey, guys!

Looking at buying a 4.0L WJ (a rare Limited-spec'd Laredo w/ part-time NP242) with 140k miles. Build date is 07.11.1998 (MY 1999), Texas delivery.

Will this vehicle have the infamous 0331 casting head?

I have been reading contradictory information about the very first WJs (1998/1999s) having this spec. It seems it's consensus, that the TUPY casting upgrade came about mid-year 2002 for the WJs.

Appreciate all comments.
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Old June 23rd, 2022, 02:55
Ralph77 Ralph77 is offline
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Re: Will a 1998/99 WJ have the 0331 head?

I always assumed that even though a 0331 head in an XJ is a '00 and '01 thing that you would find them in the '99 WJ.
I believe that you can see the head number poking out just under the valve cover.
Also to see if the head has been swapped the TUPY is supposed to be clearly visible through the oil filler cap.
I also guess that by what exhaust is on the WJ that you could tell too.
2 piece exhaust manifolds would mean a yes to me.
Also the dual front cat, CA Emissions, or the Y Pipe with Federal Emissions.
Also my understanding is that the TUPY head is a later '02 to '04 thing.
Also later '02 to '06 TJ thing.
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Old June 23rd, 2022, 09:04
smokeyyank smokeyyank is offline
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Re: Will a 1998/99 WJ have the 0331 head?

Early models would not have the bad head. It was the late 00 through early 02 that it would be more prevalent. You can open the oil cap and look to be sure.
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Old June 23rd, 2022, 16:28
NXJ NXJ is offline
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Re: Will a 1998/99 WJ have the 0331 head?

Thanks, guys. I guess the doubt persists. Will buy it regardless and let you know what I find.
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Old June 27th, 2022, 12:36
NXJ NXJ is offline
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Re: Will a 1998/99 WJ have the 0331 head?

Here's sort of an update for this sorry saga:

https://www.naxja.org/forum/showthre...#post246758668
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Old July 19th, 2022, 09:41
NXJ NXJ is offline
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Re: Will a 1998/99 WJ have the 0331 head?

I thought I'd update this thread, as I finally pulled off the valve cover.

But alas, it's still unconfirmed. The head is stamped with "NHI", "1999" and "WJ" between cylinder 1-2, 2-3 and 3-4, respectively. Outside of the valve cover, on the manifold side, it also reads "203".

So, no reference to 0331 or 0630 that was expected. Any takers?
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  #7  
Old July 24th, 2022, 14:35
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Kittrell Kittrell is offline
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Re: Will a 1998/99 WJ have the 0331 head?

The WJ seems to have no actual reference to the Grand Cherokee and appears to be a coincidence. You'll find WJ cast heads in XJ's and TJ's as well. Though no one has ever been able to figure out what the NH is in reference to you find variations of it, NH1-NH5. What is known is that eventually (2002ish, somewhere between Oct 2001 and Apr 2002) the WJ's did get TUPY marked heads. If you have a WJ before that time, it's going to be an undesirable 0331 head, no WJ's received the 0630 head. They stamped TUPY between cylinders #3 and #4, which is right where the early heads cracked. This was likely to make it simple to identify during inspection at the dealer.
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Last edited by Kittrell; July 24th, 2022 at 15:25.
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