if the hole that goes from the vac. pod to the pri. venturi is blocked or not drilled all the way thru the sec. will never open.If you tune a 3310 carb right it will be only a few hundredths difference in the sixty foot compared to a double pumper.There is some things you can do to make the sec. open so fast you will need to install a 50 cc pump on the carb to overcome the bog.