the 0331 head thread (help out if you have one!)

[Mopud]

Here's mine, from a 2001 TJ. It lasted roughly 90,000kms (about 55,000mi). It was a difficult find because the symptoms were not that distinct, I was losing water but could not find any leaks and the car would occasionally get hot on a crawl or at idle. On a couple of occasions the car would stall but so inconsistently it had me baffled. I had the cooling system serviced and checked numerous times and replaced quite a few components; it was only until I had a combustion leak test done by checking for exhaust gases in the radiator that a very slight amount of gas was detected. I instantly ripped off the cylinder head and found some yuckies.

At first it just appeared to be a blown head so I sent it into the machine shop for service. They found some damn nasty cracks as you will see below..

Water in the head and obvious signs of a blown head..











The machine shop found these cracks after I asked them to take a look at the head and open up the ports a little bit with some mild porting..











I've also just blown a 0630 head but have a 7120 on the way to begin my 4.7 rebuild ..

Hope this helps some...

Mopud

[SilverXJ]

Wow.. usually the crack between cylinders #3 and #4 but that thing just cracked all over. What were your engine temps?

[Mopud]

Honestly I don't remember, this all happened back in 2008. Freeway speeds were normal at just under 100 degrees, at idle the needle would creep over. I think only on one, maybe two occasions did it hit the red.

Only now after two blown heads have I invested in an engine watchdog and also a scanguage2 to keep a better eye on things!!

[1bolt]

Ouch if I was you I would definitely check the mains while the engine is down...

[Huck]

So after reading the last 5 pages should I believe that my 06 TJ head is not prone to cracking? I ask because i want to build a mild stroker out of this motor.

[Mopud]

Yep you're safe Huck, at least safe from cracking from a known manufacturing fault

[NorCalChris]

So what has been decided on the 0331 head? I know that if it has TUPY it is safe to say it is good to use, but as far as performance goes compared to a 7120?

[brotherwes]

Very interested in this topic ... no posts since Sept 2010???
If I understand what's been said, my 1999 XJ should NOT have an 0331 head, right? Will have to take a peek this weekend...

[WJ 2000]

Ok heres mine @ 196.375 miles and still looking good

[Root Moose]

I have two Jeeps down with cracked cylinder heads (2000 and 2001 XJs).

To source a replacement it seems like Alabama Cylinder Head and Clearwater Cylinder Head are trusted sources for replacement heads.

Are the heads they sell TUPY heads?

Are there others suppliers worth looking into?

[Root Moose]

The two heads I received from ACH do not have TUPY cast into them. I take it these are their own casting?

[Alex22]

The shop I work for has ordered two new castings to replace cracked 0331 heads. Both heads have been from "liberty engine parts." I'm not sure who is casting them for Liberty but they are definitely new castings, the ports are a bit different and not as nice as the OEM heads are. I haven't seen any other new castings so I can't comment on them.

~Alex

[SilverXJ]

ACH uses some kind of reinforced casting of their own, not TUPY.

[hot_rod_hooligans]

2001 XJ, 175,000 miles, #6 piston skirt failed causing a crack in the cylinder wall.




You can see here where the piston was slapping the head after the skirt gave.

Castings

[Retlaw01XJ]

They obviously have the year cast into the head.....
The other number, which range from 017 to 347 in the pics in this thread, could be the 'day of year' date code.... 017 would be January 17th, 180 would be late June, 365 would be Dec 31st, etc.
I have a 2001 XJ with '269' and '00' cast in the head....translates to late September. Sticker on the door says it was built 10/2000. It's a fairly close match. How about the rest of you? Does truck build date correspond to the 'day of year' number on your head?

I'm gonna pick up an '04 head this week....hope there's a tupy or an '04' on it, or I'm gonna pass on it.