1984 XJ Pioneer 2.8 liter engine tapping

Just fishing for a specific cause of a noise here. I have a stock 1984 XJ Pioneer with the 2.8L, V6. When the engine is cold and warming up it is quiet. When the engine gets operationally and normally hot, there is an insistent tapping from the engine. The engine runs well enough and there is no unusual leaking and no overheating even on these upper 90s days we've been having in the east. When I put the stethescope on different points of the engine I can reach from above I hear nothing unusual but when I put it in the oil fill pipe I hear the tapping very clearly. Any ideas as to the specific problem? Thanks! David

excess clearance in the valvetrain is most likely. Pull the rocker covers and see if you can determine which rocker arms and push rods have play.

It could also be the timer for the time bomb that most 2.8L engines came equipped with. It was located just aft of the #2 rod journal IIRC:wave1:

Thanks!