Edelbrock 1406 whistling

Rob I ran into this on a car, Same symptoms, it was the intake flange barely cover the base of the carb. It sealed for a while but then started to whistle after time. The fix was a gasket that fits the intake , then a spacer or plate that fits the carb base and then a gasket that fits the carb. Make sure your gasket is sealing both.. Take a piece of paper and set it on the intake . press around all of the edges to make an exact copy of the intake flange, inside, outside and bolt holes. set this on the bottom of the carb and make sure it covers all of the carb flange. If it does not you need a steel plate or an aluminum spacer to compensate for the difference and two gaskets one on each side of the plate or spacer. also spray around the intake I have seen the intake gasket whistle . If you put a large port intake on a small port head and used the small port gaskets. The gasket must match the intake. Looks like you have a 340-360- intake and you mentioned this is a 318. this could be your problem. and just by coincidence you are giving it fuel at the shaft and compensating for a greater leak. Just thought I would mention this also because the first pic is not the same intake as the rest of the pics? If it is the intake, Another thing that most do not do when bolting a different intake on is to port align it. Take a straight edge and scribe a line directly between the ports up to the top and continue this line around the top side. this is the center of each port. You'll notice there is not much room for error. The valve cover bolt holes are in the center of the ports on the head. Set the intake on dry and see if they are close . you can slide it front it or back to get them equal . If one is off an 1/8 and the rest are center you can slide it a 1/16 and make them equal. This is why new intakes are not drilled for the end pins. When you find your best location for the intake you tap down on the ends with the pins in place they will leave a mark and this is where the pin holes will be drilled. That then makes this intake alignment specific to this motor. But remember small port intake gaskets will not permanently seal a large port intake. That is more important. The alignment is only a suggestion for person who really wants to do it once and get the most out of his modifications .