I did a periodic check underneath the valve-cover, and found a "rocker arm" was broken. The main piece was resting next to the intake valve spring on the front cylinder passenger side. I found the remaining pieces in the oilpan. The cams are perfectly smooth. Nothing else seems to be damaged. Inspecting the hydraulic lifter I decided I want to replace this as well.

Q: Is there a way to install the new rocker and that little "washer" on top of the valve, without first removing the intake camshaft??