Too much fuel pressure?
Or float or float level
Or needle and seat are leaking.
Take carb off car. Drain all fuel. With carb upside down by mouth blow into carb inlet it should be all restricted and you can't blow through. If you can blow through the flaot is not closing the needle to the seat or the needle and seat are bad. TRy first spraying some spray lube on them after you remove them and re-install and upside down the carb and again blow. It should seal. IF not buy new needle and seat and buy either the steel or the viton. Viton is best with most fuels.
When you get the needle to seat so you can not blow freely through with carb upside down. That part is done.
Next you should be able to adjust the needle and seat up or down to postion the float so float is slightly below the sight plug. If not you will need to mabe bend a little tang on the float some so it will adjust right.
When you get it right the fuel level will be just barely below the sight plug. You get this by adjusting to barely see the fuel at bottom of the sight plug. Then turn the flaot adjuster down by 1/2 turn.
The right fuel pressure is the pressure that is just below where the fuel blows by the seats.
Ed