[dataway]

Just watched that video again about ten times ... jeez, I'm going to go against the grain and say it's coming from the front of the engine. I assume you've removed all the belts and ran the engine and the sound remains? Like others, I think it's half engine rpm since it's almost slow enough that you can count them. Any chance the timing chain could be contacting something? In my mind a see a picture of a bad chain link on a double roller slapping the nose of the oil pan ... but I don't think it's close enough to do that.

Other than the noise ... engine sounds great, very healthy and strong.