Miles per gallon?

Something is wrong.

1. Either you do not know how to drive for mileage or something is wrong with the tune. Just enough pedal to maintain speed. Hold the pedal steady, do not accelerate or decelerate unless needed. The accelerator pump is just pumping fuel into the carb. Try getting and using a vacuum gage, the higher the vacuum the better the mileage.

2. Engine not tuned for optimum power. Adjust the valve lash. If original, replace the points or adjust the dwell to specs. Replace the cap, rotor, platinum spark plugs, and get good wires (I use Taylor Spiro Pro). Check the vacuum advance to make sure it holds a vacuum. Adjust timing. Start at factory specs 2.5 degrees before Top Dead Center. Take a trial drive, up hills at part and full throttle. Keep bumping it up, 5* BTDC next, till it feels the best or pings. If it pings back off a step.

3. It is hard to get a constant mpg around town. Constant cruising at highway speed with little change in acceleration is where you get the big numbers. My best slant got over 30 mpg. That was highway, and that 170 was not stock.