Check your cam gears.

 

Yes, I've seen those come loose.

 

Yeah, i had this happen firsthand. I now properly torque them to spec with a torque wrench every time they are removed .

 

I use a torque wrench AND blue loktite!

 

I checked the cam bolts today. They are tight. I removed the valve cover and from my extremely limited knowledge of engines, everything looks ok here.

A few pictures are attached.

The sound is definitely coming from the engine. I have a stethoscope and I cannot pinpoint the location. It sounds very similar along both sides of the engine. Here is a video from today for sound:

 

Did you actually install a new head, cam, and lifters? You notes in the video mention that, but I don't see anything in the thread to that effect...

Sounds like a valve train issue to me. I had a MB AMG C63 with some bad valve buckets/lifters which sounded very, very close to that sound. Some of the cam lobs look wore, which could create excess lash between the lobes and valve buckets. That will cause a dreadful racket as the cam lobes smack the tops of the valve buckets.

collapsed lifter or stuck valve 1.6 na - ClubRoadster.net

VIDEO0003_zps939e2594.mp4 Video by j-radvw | Photobucket

If it isn't a cam lobe problem, then could be a bad HLA lifter or valve problem. Check out this post on CR and the linked video. The tapping in the video sounds very close to your engine...

From the last video, it sounds like the valve cover is amplifying the tapping noise. When the camera drops below the height of the valve cover, the intensity of the noise decreases. It it was a connecting rod bearing, I would expect the opposite.

Some other basic troubleshooting ideas...

Compression test
Change oil, check oil and oil filter for metal shavings

(A bearing issue in the short block would put metal into the oil and oil filter.)

 

I have not replaced any engine parts yet. Thanks for the examples. I will look into those.