My Grand Cherokee  a couple of weeks ago started making a tapping noise and it was bothering me big league, so I concluded it wasn't worth pulling the head at 200K miles..instead replace the whole thing with a fresh complete rebuilt long block all new parts inside bored .30 over etc.... Yesterday we yanked the old one out and our goal is to put in the rebuild today......at least on the engine mounts and attached back to the trans. I guessed wisely it wasn't head related, it was piston number 6, it had cracked a chunk off the bottom of the piston itself! I will report back.