Edelbrock 1406 whistling

I believe the plate you used is alluminum. It is soft . You need to use a 6061 machined .250 thick plate and black felpro gaskets. also are you sure you didn't spit a lead plug out of the base of the carb. or a rubber plug off of a vacuum tube. Take the gasket the you are using between the carb and the plate and hold it to the bottom of the carb. Make sure it covers all of the carbs diameter. Now take the second gasket the goes between the plate and the intake and set it on the intake . Make sure it covers the intake opening, Now those gaskets should be the same as the plate that goes between the two gaskets. If all these things match and the plate is not a thin soft alluminum peice, it should seal. I have an actual adapter second in from the right in bottom row. You Pay the shipping Steve