Fuel Evaporation

I have to crank for a few seconds to start my '65 Cuda after it sits for a week or two. When I shut it off after a drive, I smell gas fumes. I believe I have a problem with fuel evaporating in the carb. Originally I thought fuel was leaking from the carb so I pulled the air horn and filled the bowl with kerosene and let it sit over night. The next morning the kerosene was still there. I'm thinking about placing a spacer under the carb to better insulate it from engine heat. Does anyone have any other videas about this problem?