Stumped - Strange Noise

[Bushman66]

Got the Chevrolet 350 Crate Motor up and running, but me and all of my buddies are stumped. There is a grinding/growling noise coming from what seems like the top end of the engine. The alternator is new, as is the water pump. When we took a folded blanket and covered the distributor, the sound was gone.

So...ordered a new (remanufactured) distributor, a new AC Delco cap and new rotor. Reused the new premium Accel points set out of the old distributor. One thing I noticed when I removed from the old distributor was that the fixed post of the Accel points set was bent, and I definitely didn't drop them. Took a pair os smooth jaw pliers and bent them back to parallel.

Installed the new distributor, timed it up and...I STILL HAVE THE GROWLING NOISE. Oil Pressure is good, throttle response is good, and the engine sounds healthy.

I'm totally stumped at this point. Ordered a mechanics stethoscope to see if that would help.

Brand new Edelbrock AVS2 carb. Edelbrock Performer manifold. Tall stamped steel chrome valve covers took one off, no obvious valve train noise or interference with the valve covers.