I would cancel the order of a head gasket. It is completely useless to remove the head if you don’t know where the problem is.

From your description I would suspect a hydraulic valve adjuster, easy to diagnose without taking the engine apart. Those adjusters have a small sealing ball in it to retain pressure. If this does not work properly it will give the symptoms you described.

Just remove the valve cover and feel all the rocker arms, you will have to turn the engine, the clearance can only be measured if the cams are opposite of the rocker arms. Disable the ignition if you use the starter engine to turn the engine, if the engine start the oil will spray out (a lot of it).

It takes only a very small debris to let the adjuster malfunction. If you can move the rocker arm the adjuster is defective. They are easy to replace and not very expensive.

Noise from a bent rod or damaged bearing will not go away and the tapping (mostly more violent than that) will be at twice the speed of the ignition and change under load.

Tapping from a adjuster will be at the speed of the ignition and will not change under load. If the sealing ball still works somewhat pressure will build up after some time and the tapping will go away.