I own a 98 zj (4.0) and i have a rod knock but I want to swap my head with a 2000 WJ head its 4.0 as well. Will the bolt holes line up correctly? Or am I better off sending my head in to get rebuilt? Yes I pulled the VC off and the 3 rockers are lose (not crazy lose) no rods dropped. So I figure i better do something before it turns into an even bigger mess.

 

I don't see that as a head issue. Cam,lifter or pivot fulcrum maybe. How loose? If lifter bleeds down and valve is completely closed it will feel a LITTLE loose.

 

The answer to your original question is yes, it will fit. See if you can score the intake manifold as well. It flows better than your old one.

 

i didnt get any vids of it with the vc off, but heres what she sounds like. When i rev I can still hear the tick, it increases with rpm. I threw seafoam in her and it made it even worse, but when i pulled the vc off everything was clean no gunk no nothing. Then i put the vc back on and did an oil change castrol 20w50 thinking thick oil will tone down the knock.. NOT. I want to throw a new engine in her but im short on money :/. I bought a lemon lol Not happy

 

For me as I watched the video, sounded like the noise of a lifter. I wouldn't recommend to use any other oil viscosity than the factory, every parameter like oil pump flow, bearing clearance, and so on, is optimized to that, and it's not going to help, just mask the real problem.

 

From the sounds of the video, that's just a normal 4.0! A thicker than normal oil will just make it louder. From what I've been told, the supply ports to the lifters are small and don't supply enough oil to the lifters at low rpms to maintain the valve lash closure. The noise usually disappears at about 1500 rpm or higher.

Valve rattle at idle is a known trait of the 4.0 and has been with us since it's introduction in AMC cars. I wouldn't worry about it unless it gets a LOT worse. If you stand next to a jeep that's idling, you can distinctly tell it's a 4.0 just from the sound. As a matter of fact. I would be worried if it DIDN'T make that noise.

So maybe you pulled the head for nothing.

Welcome to CF!

 

I tend to agree. On a cold start it can take SEVERAL minutes for oil to get to the top of the engine, and like Dave said thicker oil exasperates the problem. However, once rpm is increased and oil pumps up lifters, the lash should not return at idle unless lifter is leaking down. Once a lifter pumps up it should stay up.
The 4.0 is not a precise modern day engine and a little valve lash does not hurt anything. Us old timers that were around when most cars had solid lifters instead of hydraulic can tell you about NOISY engines!

 

Yeah, this engine started it's career in AMC cars in the late 60's and hasn't been changed much since, however it is incredibly reliable and long lived. The only thing they DO do is crack pistons occasionally. I think the reason for that is they are cast and not forged. Don't expect any modifications to increase horsepower. It's giving it's all now unless you want to decrease longevity.

 

Whatever head you use, make sure to check for warpage before re-installing and use new head bolts. I have a brand new in the box set of FelPro ES71102 head bolts if you're interested.