Trying to figure out THIS noise. Options

[Rob-O]

At its loudest when I pull to a stop and the car is idling. After 20 seconds of this sound at idle it usually goes away. Revving the motor gives mixed results. Sometimes the noise rises with the rpms and then goes away. Other times it goes away almost immediately when the rpms start to rise.

I thought the oil level might be low and I was starving the motor but oil level is fine. Of course that doesn’t mean that the oil pump is pumping volume but at least the level is fine.

Only things that I’ve changed or adjusted before the noise started were:

1. Changed to a different AFM. Thought this might be detonation but the mixture screw is turned all the way in. So if anything it should be running rich with the mixture screw all the way in.

2. Timing was checked and adjusted. This noise is present at 8 deg. BTDC (stock setting) and 4 deg. BTDC.

3. Added heating ‘j’ tubes, flapper boxes and the rest of the associated hardware to the drivers side. Incidentally it *almost* sounds like the noise is coming from the drivers side. I thought it could possibly be the small flap that cuts off air going to the heat system at idle. But it just sounds too loud for that and even if it was that flap would really have to be snapping back and forth a bunch.

https://youtu.be/ELe26KeljpU