I just read through this post and I still have a few questions, Jim you will have to chime in here because I havenÆt taken my 4.0 apart yet, but are all the rockers on a common rail or do they have individual mount posts like a Chevy? If they are individual I would pull the rockers on the bad cylinder and see what the push rods look like. The only thing I am really curious about is, Is the valve on the ôlooseö rocker actually closing all the way? Have you done a compression test? I didnÆt see any numbers for what your compression was across all the cylinders. I would be really hesitant to mix and match used parts because as Jim said they will wear on each other faster because they are already worn in. Have you taken any pics of the head? Maybe something will jump out visually that you are not seeing.

Sean