Popping thru carb
Have used this stuff before
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3-4 mm makes a surprsing difference and that thickness doesn't usually cause the air cleaner nut to ding the hood
draw round gasket, cut it out with a small cutting disk, drill stud holes bolt it onto carb after using engineers blue or wet marker pen on carb base so you can print the shape and position of the bores. centre punch hole saw and away you go.
i just glued it to the manifold with coppacoat gasket spray and used the gasket on top
two gaskets probably the best bet
Dave