Hi y'all.

I have 2 Grand Cherokee Laredos.

1 is an 04 with the 4.0 straight 6
2 is an 02 with the 4.0 straight 6

The 02's engine has a cracked head. The 04's head is good. The 04's block is crap. The 02's block is good.

My question is... Can I bolt my 04's head onto my 02's block without any problems?

The reason I ask is, because the frame on my 04 is broke. The 02 has almost zero rust.

 

Yes.
Will be a straight bolt on.
Guessing your '02 was made early in the year so it has the 0331 head in it.
When you take the valve cover off the '04 you will see the letters TUPY.
I think people say that you could see the letters through the oil filler cap.
It is still a 0331 head just the improved version.
Some '02's made later in the year will have the TUPY head.
And the rest of the WJ's from that point on.

 

How do I know about my 02? I'm just a wrench turner. I don't know a while lot about specifics.

 

How do you know what about the '02?

 

How do I know about my 02? I'm just a wrench turner. I don't know a while lot about specifics.

 

How do I know when it was made. I'm asking because I'm being told that the gasket set I want is compatible with the 02 but not the 04

 

White sticker on the driver's side door will tell the date of manufacture.
By the way this is the XJ section and you really want to ask this question in the WJ section.
I just happen to know the answer because I have a TUPY head from a '04 WJ as a back up for my '00 XJ.

I went to take a look at Napa online for both vehicles.
They do ask for a letter from the VIN for both '02 and '04.
I went back and forth trying both years with both letters and I come up with FPG 26211PT.
Wondering if they are looking up the part wrong. V8 for one and the straight six for the other.

 

There should be no difference in head gaskets for a 4.0L except early ones don't have dowel pin locators in the block for the head, but can still use late model gaskets. There's nothing the 04 has that the 02 doesn't. Well, maybe thickness. Don't be going with a thicker gasket! It can change your lifter preload.

 

Amen. I will add, it WILL change your preload, and drastically. Mike the old one, and put the same thickness back on.