Concerning gas mileage, with my 140 Corsa 4 speed, I usually get between 18-20 mpg. driving in metro Atlanta, Ga. On the highway, I have been getting between 27-29, if I stay under 70 mph. My Corsa does have a 3.27 diff and I do have a Dale recurved distributor. Dan Terry '65 Corsa 140 Coupe Corvair Atlanta