Probably not vapor lock since vapor lock occurs on the suction side of the fuel pump. Any pump will push fuel and any vapor easily, but cannot pull vapor. Any 'treatments' between the fuel pump and carburetor are useless. When vapor lock occurs there is total lack of fuel after driving a a few hundred feet and the engine dies.
Most likely what is happening is percolation where the gas in the carb boils and dumps into the intake manifold. In the severe form the engine will appear flooded needing prolonged cranking when trying to start 30 minutes later or if set overnight the carb is dry and requires prolonged cranking to fill again; less severe will flood the air bleeds in the carb and there will be rough running a hesitation until that clears. A spacer under the carb will help with percolation.
Bookmarks