I got the damper off as discussed in separate thread. Removing Harmonic Balancer Thread. The sound remains while running up the idle for 3-4 seconds. Dang!

While cleaning up the timing gear case for removal I noticed what's in the picture. Two loose nuts on the front motor mount bolts. The engine was sitting on studs and not bolted down. Could this be the problem?

Nope. Sound persists after tightening up the bolts.

Next. Drop the pan, take off the timing gear cover, look around and get back to you.
Attachments
Motor Mount Front.jpg (27.4 KB, 194 downloads)

Last edited by Wally / Montana; 08/16/2020 2:39 AM.
1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.