carter afb: fuel disappears?

I have an older carter afb that a friend gave me. Its a 750 cfm. When left for a week or so after running the car there is no fuel in the float bowl. I rebuilt it before I installed it on the car and I have taken it apart a few times to check everything out and clean it. As far as I can tell everything looks normal. Is it leaking out and eventually contaminating the oil? The car runs great after I get gas in the carb. If it is leaking, does anyone know how I can fix it? Thanks.