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Old 05-04-2012, 04:06 PM
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proper fuel line diameter

I am building a 48 Chevy P/U frame up. I am ready to box the frame and want to run the fuel line inside the boxed frame. The tank will be in the rear of the truck under the bed. So it is a long run to the engine. I need to decide the correct diameter fuel line that will support an engine with app. 400 to 500hp and anything else i should or should not do to prevent any problems down the line.

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Old 05-04-2012, 05:00 PM
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It really has a lot to do with the pump you are using than the line size. The line induces pressure drop (the longer the Fuel Line, the more pressure drop), or resistance to flow. On a suction systems, ie, mechanical pump, the fluid from the tank is not pressurized, so it is harder to move than say an electrical pump back at the tank that is sending it to the front of the car under pressure. It would be better in that situation to use bigger line to make it easier for the volume of fluid to get to the pumps inlet; less suction effort. Pressurized fluid will always be able to move faster than non pressurized. Pay attention to the GPH the pump you have at the pressure your system/carb needs for the HP you have.

Typically, at wide open throttle, full power, an engine requires 0.5 lbs. of fuel
per horsepower every hour. A gallon of gasoline weighs approximately 6 lbs.
Therefore an engine rated at 500 horsepower will require about 250 pounds
of fuel every hour.
(500HP x .5 lbs = 250 lbs of fuel
250 lbs/6 lbs = 41.666 gallons per hour)

The bigger your line is, the easier it is to push the fluid without building pressure, so it really does depend more on the pump's ability to provide a specific flow rate at a specific pressure. A pump that can supply 50 GPH through -6 line at 4 PSI may not cut the mustard, but a different pump with a higher pressure rating may supply 100 GPH through the same line but it takes 8 PSI to do it and would be good enough.

This may help-
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Old 05-04-2012, 05:03 PM
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fuel line

my question is where is the fuel pump.. mechanical on side of engine or elect at rear ??? elect at rear i don't see a problem when 3/8".. on motor do a 1/2".. overkill is better then starving for fuel and u run it once. and keep the rubber lines to a min.. making sure its good for E fuel.
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Old 05-04-2012, 06:42 PM
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If I were you' while your at it, I'd run a 1/2" supply and a 3/8" return in case you may convert to fuel injection later, since your going to box it in.
Use the same mounting hole for two clamps on opposing sides. If you don't do it now while you can you may wish you had. It would be a lot harder to do later. If you don't need it now just plug the return. Not that much more expensive and gives you options in the future.
A lot of regulators use a return line. Helps keep the fuel cooler and helps to prevent vapor lock.
Then again I do a lot of things with too much overkill.
Good luck
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