Gas mileage 225 Slant 6

stretch said
I daily drive my 73 Dart (Known as the Shart because Stretch has a Dart :D).

I live in a very rural area of upper Michigan so my daily commute is a combination of back roads and 2 lane highways with 55 M.P.H. being the max speed. Its about 25 miles to work with two small towns to slow down through. I average 21 M.P.G. back and forth to work and on a recent road trip (200 miles round trip on two lane highways) I averaged 29 M.P.G..

My car is a 225/904 with unknown gears, 4 wheel manual drums and 14 x 5.5" wheels. I rebuilt the carb, adjusted the valve lash, did a basic tune up, replaced all the vacuum lines and replaced the intake/exhaust gasket. I set the base timing at 12 deg. BTDC. I custom bent a 2 1/4" dual exhaust system with two cheap reverse flow "turbo" style mufflers. I made a new down pipe and installed a "Y" to split to the duels. I also set the wheel alignment at .5 deg. negative camber (both sides), as close to 3.0 deg. positive caster as I could get while keeping the camber at .5 negative, and set the toe at 1/8" in.
I have collected the parts required to convert it to a A833OD this winter. I just need to rebuild the transmission and find a flywheel. It will be interesting to see what the OD does to the fuel mileage.

I'm about the same as Stretch here. I have 40 mile commute that is primarily highway 60-75mph and the last few miles through town at 45-50mph. I average 25mpg. Whenever I drive across the state to see my parents I get 32mpg maintaining 70 the whole 180 miles. Car is a '74 Dart Sport. Engine itself is a stock, 30k mile survivor; has a header, dual 2.25" exhaust, Clifford intake with Weber 38 2bbl. Trans is the original A230, 2.73 gears, 27" tall tire. Took the timing from whatever the factory had it set at and turned it all the way up. Maybe one day I'll check where it is. Every car is different; my '76 Scamp that started me into these cars only got 16mpg. That one was an automatic car, unknown gear, stock tire height and almost 200k miles when I sold it. But, that one was a factory air car and it worked; 9-12mpg when I used the a/c. Obviously, I just drove with the windows down.