I'm looking to fab up an aluminum plate to separate the carb from the hot engine compartment air so it gets fresh air from the cowl on my new fiberglass hood (5" cowl). I have the metal work figured out and will cut a big hole in the middle of the sheet and rivet it to the bottom of the air-cleaner base.

My question is what should I use for foam around the edges to seal against the hood? I'm looking for some "non-breathable" foam... I have some foam at work that was used as packing material but it seems air can get through it too easy...

Any of you make one of these and what did you use to seal the plate against the underside of the hood?

Thanks,

-Chris