So have a '94 4.0 with 220k+ miles on. When driving the lifters/rockers sound really noisy to me, like it's low on oil or need to be tightened down kind of noise, but only does this when it gets above 2k RPM, anything lower and runs smooth, no real noticeable noise. Can the rockers on these heads be tightened down or does the whole head need to be pulled off and rebuilt? The jeep runs fine, plugs look good when pulled so don't think I have a cracked head or anything just noisy rockers.

Also on a motor with this many miles would it be bad to rebuild the head? Would it cause in issues in the bottom end of the motor?

Thanks

 

Hello, I pulled the head on my 91 with 300k and replaced the lifters, helped a lot.

 

Maybe you could remove the rocker cover & check if the rocker arms are getting oil, from up through the push rods.. If not, clean out the push rods & open the oil holes in the rocker arms. If you do it, don't mix the parts, since they are kinda mated to each other.
Replacing lifters on a worn/used cam is not always successful, since lifters mate to the cam when new, and new ones wont always mate with the old cam.
If you decide to replace the lifters, cut the oil filter apart at the next oil change & check the paper element for metal....
It there's much metal, you may need en engine rebuild....