will this combo kill my MPG?

hemitheus said
Drop the air gap for a conventional performance intake. Dual plane is more street friendly. Single plane for more strip use.

the air gap / crosswind is a dual plane, and is the only one I have with MAGNUM bolt pattern

the 268H cam came with the 67 318 motor,

dont have a thermoquad, just an Eddy 600 and a 600 Holly off of a 1972 440 motor (came stock that year)

I am trying to use what I have, this is a very low budget deal, no money to spare,