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Old 07-03-2019, 11:31 AM   #1
The Rocknrod
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Fuel Line Size Pump to Carb

What is the consensus on the size of fuel line I should use from the fuel pump (mechanical) to the Carb. Using a 625 cfm Street Demon. Right now Iím all set up for a 3/8 tube, but I was thinking of maybe using a 5/16Ē tube instead. Blueprint Engines 350.
The fuel pressure would be the same but the volume might be more? Maybe that is over-thinking, just raising a float.
I donít know thatís why Iím asking what the general thoughts are on the subject. What do you think?
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Old 07-03-2019, 11:52 AM   #2
kwmech
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Re: Fuel Line Size Pump to Carb

Why do you think a smaller line will give you more volume? GM went to 3/8 for a reason on the V8. 5/16 was for the 6 cyl. Pressure will be the same regardless.

Had this happen to me at the plumbing store a couple of years back. I was looking for some fittings for a gravity water system I was installing. 4'' pvc down the hill from my storage tanks. I needed to end up at a hose bib with 1'' to the valve with a few Ts underground. Guy commented that by doing that I should have 4 times the pressure. I just looked at him and said you're fired. I got the weirdest look from him.
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Old 07-03-2019, 11:54 AM   #3
The Rocknrod
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Re: Fuel Line Size Pump to Carb

More volume on the larger line. Maybe I didnt write it correctly on my first post.
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1964 C10 Step-side Short Bed - In Progress
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Old 07-03-2019, 12:31 PM   #4
rpmerf
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Re: Fuel Line Size Pump to Carb

More volume on the larger line, so why would you want to use a smaller line?

3/8 = 6/16 > 5/16
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Old 07-03-2019, 12:34 PM   #5
The Rocknrod
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Re: Fuel Line Size Pump to Carb

I'm askin the question why would I need a 3/8 vs 5/16?
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Old 07-03-2019, 12:41 PM   #6
WorkinLonghorn
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Re: Fuel Line Size Pump to Carb

Either size is fine IMO. Your 625 cfm carb can only use about one once of fuel per second. That is ~2 tablespoons per second.
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