[GeneBob]

Of course, it may be something obvious like your radiator is not cooling. No contact thermometers are pretty cheap and you can check to top of the radiator (at the return spigot) compared to the bottom tank. You should see at least 20°F difference.

If you are running hot with the timing set right, you might want to check your air/fuel ratio on your carb. If you are lean at idle, your parade speeds might be too lean? If you don't have an air/fuel meter, I use the smell vs eyes burning method. I know this sounds crazy. If your exhaust burns your eyes, you are lean. If you smell sweet gas, you are too rich. Those are wildly opposite ends of the spectrum but without a gauge, you need somewhere to start. The problem with reading the plugs at idle is it takes a while to get anything on the plugs that is meaningful.