1966 Ford Mustang wont start unless I dump gas in the carb

Also, stick your eyeballs down the center of the carburetor to see if there are two nice fuel streams when you push the throttle by hand. If not, the fuel is either leaking from the base of the carburetor or it is evaporating out. After some passages are drilled in the body, lead plugs are pressed in to close up the holes. If one of those plugs are leaking, they can be sealed with epoxy. You should smell the fuel too when you get close.

When you park it at night, remove the air cleaner housing and tie a plastic bag around the entire carburetor. If the engine starts right away the next morning, (after removing the bag), the fuel is evaporating out.

A weak accelerator pump will do this too but it will usually also cause a severe stumble when you want to accelerate.

Caradiodoc