318 MAX fuel economy builds?
Back in the seventies I had an Ex police 265 hemi six Valiant charger. I put a pacer factory 4 barrel manifold on it and factory headers. Those factory 4 barrel manifolds were very long runner manifolds with a water heated plenum in them. This car ran 14.7 sec qtrs @92 mph . The camshaft and exhaust system were standard police spec. Carb was a vac secondary holley 600 cfm.
This car ran exactly the same as the original 2 barrel and fuel economy was as good if not better than the 2 barrel. The only thing I changed when taking it to the track was to disconnect the water heating and going up 2 sizes in jets.
Until I put the water heating back on after the drag racing it would have a slight dead spot off idle but the water heating fixed that.