The Stovebolt Site Forums The Shop Area Engine Shop Occasional engine knock at various RPM

Here's an update.
Haven't found the cause yet.
Timing gears are OK. Dampner is OK.
Tach says the "knock" is between 2000 and 2500 RPM.
Changed to 15W-40 oil. "Knock" is still there but a little bit less loud.
No noise at idle. No noise above 2500 RPM. No noise when cold.
Then again, I don't go over 2000 RPM when the engine is cold...
Put a new clutch in with new flywheel bolts. No change but I needed the new clutch anyway.
Does anyone have an idea what the "knock" could be?