99 4.0 head ID

Just wondering how i can tell if i have the better head on my 99. Jeep was built 2/99. the numbers on the engine sticker are worn off from engine cleaner. What is the problems with the 0331 head ? how do i know if i have that head thanks

The #0331 head refers to the casting number - I believe it changed sometime in 1999.

As I recall, the #0331 had bosses for mounting the coil rail for DIS, while the #0630 still used a distributor. The XJ did not get DIS until 2000 (I think...) so you probably still have the #0630 head. The number will be a raised casting, physically on the cylinder head, but I don't recall where exactly. I've got to work on that...

The #0331 cylinder head has occasional issues with deck cracks toward the rear cylinders, but a competent machinist can probably weld those up for you. I'm not sure if the coil rail can also be bolted to the #0630 head, so that merits further investigation (and is one of the reasons I'm collecting cylinder heads.)

While cracking CAN be an issue with the 0331 head, the odds in favour of cracks seem to be about 1 in twenty, I think, and many of those are probably smaller cracks that don't actually present until the engine is rebuilt.

If you suspect cracking, try a compression test and/or a leakdown test. If you do the compression test, make sure you A) duplicate the tests with the engine cold and at operating temperature (small cracks can close up as the head expands) and B) duplicate the tests while "dry" and "wet" (a wet compression test is done with about a tablespoonful of oil poured down the spark plug hole. Make sure you crank the engine over a couple times WITHOUT SPARK PLUGS when you're done, to blow the oil out.)

5-90

scotttruhart said:

Just wondering how i can tell if i have the better head on my 99. Jeep was built 2/99. the numbers on the engine sticker are worn off from engine cleaner. What is the problems with the 0331 head ? how do i know if i have that head thanks

Click to expand...

You probably have the 0630 casting but the only way to be sure would be to look at the top of the head on the driver's side near the no.3 cylinder.
I think the change to the 0331 head occurred in late '99. The 0331 is known to crack under the valve cover between the exhaust valve springs of the no.3 and 4 cylinders (where the head is hottest). The usual early sign of a problem is a "mysterious" loss of coolant and the owner has to keep topping up the coolant expansion bottle even though there's no external coolant leak. That's because the coolant seeps through the head crack into the crankcase, mixes with the oil, and turns it into a "chocolate milkshake".

Dr. Dyno said:

You probably have the 0630 casting but the only way to be sure would be to look at the top of the head on the driver's side near the no.3 cylinder.

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Sorry to jump in on this, but by saying "the top of the head", do you mean under the valve cover? My '99 was manufactured 06/99 which is fairly late in the model run.

Thanks,
Dave

You can see the casting no. stamped on the top of the head on the driver's side NEXT to the valve cover (not under). You'll need to lean over the engine compartment quite a bit and crane your neck to view it.

Dr. Dyno said:

You can see the casting no. stamped on the top of the head on the driver's side NEXT to the valve cover (not under). You'll need to lean over the engine compartment quite a bit and crane your neck to view it.

Click to expand...

Gotta clean the area and use a flashlight positioned a couple of cylinders away
the light at an angle to make the numbers stand up.
My VIN has an X as the 10th digit. I think it means that my 99 was built in 2000.
My head is an 0630.

falcon556 said:

Gotta clean the area and use a flashlight positioned a couple of cylinders away
the light at an angle to make the numbers stand up.
My VIN has an X as the 10th digit. I think it means that my 99 was built in 2000.
My head is an 0630.

Click to expand...

It's unlikely a 99 would have been built in 2000. They usually start building the next model year in August or September. Build date is printed separately on the safety certification label on the driver's door.

falcon556 said:

My VIN has an X as the 10th digit. I think it means that my 99 was built in 2000.

Click to expand...

The "X" indicates that it is a 1999 model. The build date cannot be determined from the VIN except via ChryCo. As Matthew stated, you can find your build date on the driver's door cert. label.

Dave