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Posted by David Sherman on Monday, August 25, 2008 at 10:56:52 :
In Reply to: Also.... posted by Adam on Monday, August 25, 2008 at 03:46:35 :
The size of the fittings makes no difference on the pressure so long as the flow rate isn't incredibly fast. Think about the plumbing in your house. The main in the street might be 8" cast iron. The pipe coming in from the street might be 1" black plastic. The pipes within the house are probably either 1/2" or 3/4" copper, iron, or plastic. The pressure is the same everywhere in the system unless you're drawing a lot of water out of one spigot.
An extremely small pipe is all that's needed to supply the fuel needs of an engine (look at the size of the main jet in a carburetor). The difference between 1/4, 5/16, and 3/8 plumbing is insignificant at that rate of flow. The fuel pump "works against" the back pressure created by the carburetor float tending to close the needle valve. The size of tubing has nothing to do with it. Too much pressure and the float can't exert enough force to push the needle valve closed, and the carburetor bowl overflows and floods the engine.
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