Quote:
Originally Posted by Bolts
GM do you mean the bypass pipe comes off the pressure side of the pump and runs back to the fuel tank to enter above the fuel level with the pressure drop on the return line being enough to provide fuel pressure at the carb?
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If you remove the fuel line at the carb and crank the engine you should get a full 3/16" diameter stream that shoots out about 12's. This is more full than the carb will ever use. Ford determined the "line size" at 3 to 4 lbs pressure needed to be .098 if I recall correctly. They tried up to .108 and down to .090 or somewhere in that range. The small diameter didn't provide enough fuel at high speed and the large diameter opening caused the bowl in the carb to flood over the top. The .098 was the size settled on for the Stromberg carb. Through a given size hole only a certain amount of liquid will flow AT CERTAIN PRESSURE. Increase the size of the hole OR the pressure and more fluid flows. At 60 MPH lets say an old Ford burns 4 gallons going 60 miles. At this rate the needle valve is operating in small motions keeping the fuel at a fairly even level in the bowl. If the pressure was way down to 1 lb the carb would most likely be starved of gas at higher RPMs. At 5 lbs the needle valve would probly still hold the float level even though more fuel is available. Much above 5 lbs and the carb would be over flowing from the bowl and run real rich. I'm using the 5 lbs as a guess and it could be a higher or slightly lower number. To answer your question there is more than twice the amount of gas available to the carb than required. You could run dual carbs and maybe 3 carbs from a stock fuel pump under normal driving conditions on a stock engine. That's where I guesstimate a return hole of from .100 to .125 will be in the area that will work. With the test set up still on my 39 I have a "T" fitting installed ready to test a return line. Will post the results after I try it. I don't have to wait for real hot weather to see if the return effects the engine running only need hot weather to see how it relieves the vapor lock. G.M.