318 fuel mileage

factory 87 police gran fury highway patrol drivetrain in a 66 more-door dart. 318, 4 barrel holley 4175, MSD 6A ignition, lockup converter 1800 stall, 2.94 rear end with 13's. best i ever averaged was 18.4 from missoula MT to spokane WA, within 7 hours round trip. most of it was at 65 mph and a steady 17 in/lbs of manifold vaccuum. my ol stewart warner motor-minder gauge really helps on long trips.