I'm doing things in order of ease and not necessarily in order of likelihood of the problem. I'm running out of easy things to do.

Thanks, Dusty. Here's my 16-year old timing gears for comparison. I'd say they look pristine. I turned the flywheel and the gears looked great all around. I can't see any scrape marks there or on the inside of the cover.

I dropped the oil pan, of course, to get at those 2 bolts to the timing gear cover. Things look OK to my amateur eyes. There is a tiny, tiny bit of end play in the connecting rods (1/32" maybe) but I think you want some.

So, what do you suggest I do next?

This is gone on for a while so I'll put on the video/audio again.

Thanks!!!
Attachments
My Movie Knock.mp4 (1.51 MB, 20 downloads)
SHA1: e0fc8c00c03e7fe9e896bc830aa131907d4720c1
KnockSound261.mp4 (4.61 MB, 12 downloads)
SHA1: a1a7bf2030045e638c9061d0f532963b9bcb8fd4
Timing Gears 1.jpg (45.53 KB, 117 downloads)
Timing Gears 2.jpg (45.18 KB, 118 downloads)

Last edited by Wally / Montana; 08/16/2020 11:21 PM.
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.