My first carb I sealed the top and bottom of the spacer with Hylomar and I dont think I helped anything by sealing it. My second engine, I made sure the mating surfaces of the spacer were flat. If you look at them, it appears they are hand finished to remove any high spots. Then I loaded the bolts up with loctite and just tightened the bolts enough so that the carb would not rotate anymore. It has worked great for me so far with 3/4 of a gallon through her.

Andy