[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.

[mgarblik]

I guess my feeling is we have a "new to the Pontiac hobby" guy who has stated many times in the 300+ posts that he is new to engines and so forth. He has good people around him helping and a good engine builder thousands of miles away unfortunately. The engine should not be making this noise. None of us, myself included seem to know what it is, but it's not normal and IMO should not be ignored, especially on a new build. I feel ultimately, although a big PIA, he will be happier having it returned to the builder and corrected. We all know it will be some dumb little thing. But if ignored, it could become a big thing. I feel bad for everyone involved because sometimes these things just happen and they can be infuriating.