The Ford Barn

Purdy Swoft · 12-22-2011, 10:39 PM

The last that I checked gas mileage, my dual updraft setup with 5.9 comp. and 3/4 winfield cam was getting 20 mpg. That was on a long run at a steady 50 mph with good gas without the ethanol. My completely stock late 31 tudor with professional rebuilt engine running a Zenith sidebowl carb, driven under the same conditions only gets 17 to 18 mpg. I have heard that others with dual updraft carbs also get better gas mileage. I know that this may sound wierd. The only explaination that I can imagine is that the model A is starving for fuel, anyway. With one updraft the draw through the one carb is stronger and contributes to more gas burned. The better manifold design, better distributes the fuel for more efficient combustion. With dual down draft carbs, unless you have a professional setup, the model 97 and 81 carbs are famous for leaking. The model 94 is a better design but much larger and if not jetted just right probably won't run at all. You need to know what you are doing with any carb setup, but the dual updraft setup is the easiest by far.

12-22-2011, 10:39 PM	#21
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: engine redo The last that I checked gas mileage, my dual updraft setup with 5.9 comp. and 3/4 winfield cam was getting 20 mpg. That was on a long run at a steady 50 mph with good gas without the ethanol. My completely stock late 31 tudor with professional rebuilt engine running a Zenith sidebowl carb, driven under the same conditions only gets 17 to 18 mpg. I have heard that others with dual updraft carbs also get better gas mileage. I know that this may sound wierd. The only explaination that I can imagine is that the model A is starving for fuel, anyway. With one updraft the draw through the one carb is stronger and contributes to more gas burned. The better manifold design, better distributes the fuel for more efficient combustion. With dual down draft carbs, unless you have a professional setup, the model 97 and 81 carbs are famous for leaking. The model 94 is a better design but much larger and if not jetted just right probably won't run at all. You need to know what you are doing with any carb setup, but the dual updraft setup is the easiest by far.