Could a head gasket cause a tapping?

[Ieatcamaros]

If all the plungers are hard, then they are primed and you have other problems or just a noisy valvetrain as menitoned earlier. If they are not hard, proceed.
You need to put your lifters in a can of oil. The oil level in the can needs to be higher than the hole in the side of the lifter. I like to use a pushrod for this procedure too. Put one lifter in the oil and (since it is a roller this will be a little harder to do) push down on the plunger part. Let it come back up. Repeat until hard(solid). Do each lifter this way. This will eliminate the lifters making racket. Btw, the travel on a hydraulic lifter is only about .075". So don't try to over do it.