I have a '69 with an Edelbrock aluminum intake and carburetor (basically a Carter AFB by Edelbrock). After it sits for a few days it requires 5-10 pumps on the gas pedal before cranking to get it started. About the same with my '65 Corvette (real Carter AFB). Both cars 'smell-up' the garage with gas fumes for a few days after they're parked. I'm told that fuel evaporation like this was not uncommon in the 'old days'; we are just not used to it with modern fuel injection and electric fuel pumps...