Need help identifying this sound. 2 videos included.

[hondaman]

1981 C10 RWD.  Brand new GM Goodwrench motor I just finished installing.  It's pretty much complete now except the odds and ends.  Including figuring out what this sound is.

Two videos.  One from the passenger side front tire, one from inside the engine compartment.  I can hear it best either standing 20 feet away from it in any direction, or directly behind the rear passenger wheel.

The noise frequency increases and decreases with RPMs

[zieg85]

Try spraying some WD-40 or something like that on the fan belts

[Irish_Alley]

can see the vids right now (firewall), but could it be the torque converter bolts being loose?

[bake74]

     The first video sounds like metal hitting metal when rotating, as Irish said or the fan blade in the engine compartment.  The second video is not very clear, it sounds more like a vacuum leak in that one.

[VileZambonie]

The video showing the timing light doesn't help. Sounds like it's whistling in the exhaust. What kind of headers are you running? Do they have plugs in them or an O2 bung? How about a few pix

[hondaman]

The video showing the timing light doesn't help. Sounds like it's whistling in the exhaust. What kind of headers are you running? Do they have plugs in them or an O2 bung? How about a few pix

They are hedman headers.  There is no o2 bung or plug.

I unbolted the torque converter today with no change.  Here are is another vid taken today

And one more taken from further back under the truck.

[VileZambonie]

I'm going to say the same thing I said in my last post here. Pix of your exhaust/engine please, the sound is common when there is an intrusion in the exhaust similarly to when you blow across a beer bottle it makes a hoot or a whistle.

[VileZambonie]

Also, if you take a mechanics stethoscope or a screwdriver handle to your ear and hold it to the exhaust you should be able to pinpoint which side it's coming from.