340 marbles rattling around 2200rpm

[RUNCHARGER]

Which advance springs are in the distributor? Depending on fuel I usually use one light one and one factory heavy one. What RPM does it quit advancing? If you have a pinging problem you want it to stop advancing more like 2800-3000RPM. If you have two light advance springs it will have full advance at closer to 1800-2000RPM and it will ping on marginal fuel.
And yes there is always a possibility it is an exhaust leak, bearing knock or other noise.

[Rockboyz]

Which advance springs are in the distributor? Depending on fuel I usually use one light one and one factory heavy one. What RPM does it quit advancing? If you have a pinging problem you want it to stop advancing more like 2800-3000RPM. If you have two light advance springs it will have full advance at closer to 1800-2000RPM and it will ping on marginal fuel.
And yes there is always a possibility it is an exhaust leak, bearing knock or other noise.

I have tried many combos, fuel is 93, right now I have 1 light and one heavy spring. 3200 is where it caps out at. Vacuum advance hose disconnected, I'm set at 18 degrees at idle. That's where it runs the best and still starting good when hot. 34 degrees at 3200 rpm. Vacuum connected I'm reading 31 at idle and 52 degrees at 3200. Again, 2200-2600 cruising, light load, light throttle, its a rap or a knock. Definitely not a ping. I'm guessing rod bearing. Don't know what else it could be. 

[pschlosser]

gosh, if it pings with the fuel you're using, the timing advance number you have set is too large. just saying. could be the timing chain is off by a tooth, who knows?  the number, be it 34, 32, 30, 22, is not relevant, while it's still pinging.

Engine tuning by sound has long been in use before timing lights and other tools.  Don't be mislead by a number that seems low or good, if it still pings.

[Rockboyz]

Quick update gents, So the car has been sitting, life priorities. This past weekend I decided to take the car around the block, just to see. I was not sold on the rod knock idea. After the ride, I pulled a couple plugs, and noticed to much timing. I ended up disconnecting the vacuum advance all together, set initial at 12 degrees, adjusted a/f/m and idle, took it for another ride, rap / knock almost gone. Came back, set the initial at 10 degrees, played with the carb a bit, took it for another ride, noise gone. pulled a plug and it looks like its on the money. Currently I have an FBO plate in the distributor locked at 18 degrees, so the total is 28. These numbers defy everything I read, videos I watched. so idk. car runs great. mystery. just thought Id share. 

[Katfish]

Makes sense, exactly where mine was, as posted above.
And I eventually ended up at 24 for safety, being in FL where it's hot and wanting to run 89, because I drive a lot.