Paul,
That truly is horrible mileage..if it's accurate. What a beautiful engine. I see a fuel pressure gauge, that must be for looks right. I also think I see A/C and a hi-idle solenoid tacked onto the front carburetor.
You mentioned power valves, float settings and jets. Usually, if you have carburetion problems like the ones you mention, you will have secondary problems like fuel fouled plugs, diluted motor oil or a bogging engine with sooty tailpipe and smelly exhaust.
Are you running the maximum advance you can run? I would advance until it pinged uphill and back it off a smidgen. Make sure things like tires are properly inflated and the brakes aren't' dragging. I would run the hottest thermostat you can handle...a 180 degree maybe.
Those things sound silly but they do count. Is there any chance you calculated the MPG incorrectly? Are there teenage kids with siphon hoses in your neighborhood. I can't imagine a old Stovebolt guzzling one quart of fuel every mile!
Stuart
