Trying an '04 head on an '02 3.7L V6.

[KJCrazy]

Hi all! New to this forum and my daughter's '02 KJ, but not new to Jeep forums at all. I usually hang out in the WJ side of town...

Recently, I pulled a cracked head from the passenger side of my daughter's 02 KJ, 3.7L V6. I'm trying to replace it with a cylinder head from an '04 3.7L V6.

Is this even possible to do? I know the '04 engines got a little redesign from the '02 and '03s, but every thing I've researched said the cylinder heads themselves were the same. Is this true?

I can only install the cam sprocket and tone ring in the 10 o'clock position if my '02 engine is set to TDC. I'm using the cam from the '04 head but trying to install the sprocket, tone ring, and cam sensor from my '02.

If I advance the timing and idler sprocket and position the dot between 12 and 1 o'clock, then the V6 stamp on the cam will finally point at 12 o'clock, but that indicates that the engine will be out of time.

Any help is greatly appreciated and much needed and thank you in advance.

 

[ltd02]

Think i got you on the other forum, The 04 should definitely work when you swap the sprocket/tone ring. I think the 05 was a bigger change in design but still not huge.

 

[KJCrazy]

Think i got you on the other forum, The 04 should definitely work when you swap the sprocket/tone ring. I think the 05 was a bigger change in design but still not huge.

Are you 02blue over there? If so, yeah, that's me. Everything about the '04 head seems the same.... I just can't get the sprocket, timing marks, and cam position to line up unless I throw the engine out of time.

 

[ltd02]

Are you 02blue over there? If so, yeah, that's me. Everything about the '04 head seems the same.... I just can't get the sprocket, timing marks, and cam position to line up unless I throw the engine out of time.

Yep that's me. I was 02blue here too but a password issue couldn't be resolved so made a new account.

It can be done with the 04 head on the 02. Just have to get that V6 mark on the right head lined up last. Almost tough to tell until you get the guides back on and everything in place then the chain should hold it at the correct position. I remember worrying over that one when I did my headgaskets a few years ago but it worked out. It's tough to explain though. Make sure you put the crank bolt back in and rotate it a few times to verify the orientation remains correct.

 

[ltd02]

Posted this on the other forum too:

I did this process twice, once when replacing headgaskets and once when installing a crank kit (spun a bearing). I took the guides off both times. When at TDC and removing the guides on the right side, the cam relaxed a few degrees. Didn't make any marks myself or pay attention to any "special links' in the chain. When reassembling, I just made sure the lower timing marks were aligned as you are and then had the left side (easy side) V6 straight and installed the guides. For the right side I had to guesstimate the location while installing the chain on the slightly rotated but installed sprocket. Then I installed the guides loosely and they would either hold it correctly or I'd loosen them enough to allow me to manually jump a tooth or so until when retightend the marks all aligned. Then I torqed everything down. The angle you describe sounds very much like the angle required to rotate the cam (sprocket installed) to achieve the correct positions for that V6 mark.

 

[KJCrazy]

My plated links have never been in the right spots on either head, according to the Haynes manual and all the youtube videos, and I don't know how that happened. I just figured that an '02s plated links must be different than other years and designs of the engine.

This all started when I got the KJ back from a loser mechanic that tore it apart and never attempted to put it back together. The first time I reassembled the engine, about a month ago, the idler and dampener dots were perfectly aligned, and timing this engine wasn't the struggle that I'm having now. Like I said before, this baby was running perfectly, but overheating with a cracked head.

So I figured I had an advantage by actually getting to do the disassembly myself. I'd have everything perfectly in place for the new head. Or so I thought.

So what I'm thinking is, the position of the chains don't actually matter as long as the V6 stamps point to 12 o'clock and the dampener and idler dots are in the TDC position. Does that sound correct?

I can put the chain on the right side, with the V6 stamp at 12 o'clock, but only if my paint marks are two teeth off from where they were when I removed the '02 head. That's with the tensioners completely removed from the engine.

Thanks for any help, again. I hope I'm not frustrating anyone.

 

[tjkj2002]

The heads are different for '04+ 3.7's then '02's heads,the compression and cams are different.

You must use both '04 heads and a '04 timing set(with '02 sprockets).

 

[ltd02]

I think it's 05 and up. Looks like the remans all fit 02-04.

 

[Aceofspades]

The heads are different for '04+ 3.7's then '02's heads,the compression and cams are different.

You must use both '04 heads and a '04 timing set(with '02 sprockets).

Side question - i been looking for a detailed thread listing differences between the years especially the 02 and 03. For example, I've heard the 02 has a timing advance feature when in 4low
Now I'm hearing the cam profiles are different and heads starting in 04.
Do you have the specs or links to where I can find out more if I want rebuild a engine over summer? Would be nice to know which cam / head combo makes the best power
Thanks

Edit. Guess I could've PM'd this. My bad

 

[KJCrazy]

I'm going for it this week and will share what knowledge I gain.

I set the cam sprocket while attached to the cam at 12 O'clock, with the chain about two teeth off from my paint marks from where it was when I did the disassembly. I'm not happy about it, but it seems to be the only way.

After torqueing the head down in proper sequence, I rolled the engine over a couple times before installing the plugs. No clinks, clanks, or interference......it feels exactly like it did when I did the first install with the cracked '02 head.

I don't know how those paint marks could be off, and I'm praying it doesn't backfire on me, but I have to proceed with some intent....It's either gonna run or I go back to drawing board number three and just keep throwing money at it until it stops bleeding....

Thanks for the help as always. Tomorrow, hopefully, the timing cover goes back on again....Intake as well...I think I might get to turn the key on Tuesday, December 19th, and then we'll have something to talk about. If this thing runs....I'll be amazed AGAIN.

I'm NOT a professional mechanic at all. I'm just a good carpenter and a DIY guy that's trying to get this done for my daughter.