Engine has 23k miles. Cam and oil pump are brand new (less then 1000 miles)

Runs and sounds normal and will drive normal with no sounds for days at a time. However a few times now I have gotten a very load valve train noise at all rpms when warm, it will sound like no oil but the gauge is between 35-50 depending on RPM. What is strange is it will go away on it's own and not come back for weeks on end. Yesterday I was heading home and suddenly it sounded like the rocker arms were falling off, I threw it in neutral and the noise was very loud at all RPMs, I pulled off at the next ramp (about a mile) and by the time I got to the stop light the sound was gone. I drove home the remaining 40 miles with no sounds.

What could be doing this?

 

Good chance of a lifter... Sound can come in and out.

Of course something could have come apart like a rocker arm.

Could hurt to figure out where it's coming from. Maybe pop the valve cover off and inspect.