If the engine has not been run in a while, you might want to tune it and run it a while.
Set the carburetor mixture to maximum vacuum at idle, then set the timing to maximum vacuum. If the idle speed increases, reset the idle speed and redo mixture and timing.
Listen for vacuum leaks. I check for vacuum leaks with a propane torch - open the propane gas until it is barely hissing. Then, carefully point the "nozzle" of the torch at all intake manifold and carburetor gaskets, fittings, and lines. If the idle picks up, you have a vacuum leak.
