Your carb is starting to percolate, probably. The cause could be the float is sinking so it does this easier. That fix is rebuilding or replacing the carb. The cause could be a lack of ventilation and another blower would help but before you spend those dollars check the air intakes. If you've done any interior work they could have been blocked or maybe full of leaves, or anything.
cold air at the fuel pump if it's on the block, the carb, and into the compartment will fix it more easily than drawing out air with a fan.
If it's percolating it will run rough and may stumble when you try to get on throttle.
It could also be the condensor, or coil, or lots of other stuff...