Street Demon carb on 1972 340 sb intake

Yeah, I never really studied things as to why its "needed" was on sons setup when he bought it, use it on mine cause they said to. I'll have to re-read the instructions for the reason they say to use it. Maybe to give better sealing on certain intakes?

If it's like the thin plate Edelbrock sells, it's to seal off the bulges on the outside edges of the secondary opening.