Mpg on a mild 360?

That .484 Purple's overlap ,doesn't help. The 750 double pumper works fine,don't tip into the secondaries. Run a vacuum gauge,keep it 62-65 m.p h.. The converter, is the" if" here. My advice: run the double pumper,don't whack it down. With today's pump gas,most vacuum secondaries need tuning time,on the primaries. (I.m.o....750 double pumper-15-17 m.p.g.).