Dark if you use the FE style dual quad linkage its possible to get decent mileage.The linkage is slotted and allows you to run on the primaries only on the front carb to a certain point,then it starts to open the primaries on the rear carb,once you reach about half throttle or so the secondaries open and then things start to get expensive[img]/phpBB/images/smiles/icon_lol.gif[/img]My brother ran this set up using a set of factory chevy 409 carters on a medium riser intake on a built 390 and says he got in the "teens"for gas mileage as long as he stayed out of the throttle.