boddvt66

My Autolite single barrel carb on my 67 6 cylinder has developed a gas leak at the vent valve rod. the car starts ok but in a matter of seconds, gas pours out of the opening where the rod enters the carburator housing.i have adjusted the valve stem rod to the correct position on the housing and the rod spring is good. what else could cause gas to back out tof his opening. thank you .Bob