What size fuel line for my application?

Discussion in 'Big Block Cadillacs' started by FauxPontiac, Jan 29, 2020.

  1. FauxPontiac

    FauxPontiac New Member

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    What vehicle(s) do you drive?:
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    I am ordering reproduction pre-fabricated fuel lines for my 1964 Lemans. My engine is .060" over 472, oversize valves, ported heads, cam is a CTA/225T-D lobe centers 110 degrees, .504"/.534" lift with stage 2 rocker assembly. Advertised duration 270/280 degrees. THM400 trans, Chevy 12 bolt with 2.73 gears. Yes, that is two point seventy three. Edelbrock Performer manifold, 750 AFB carburetor, headers. Application is primarily street use.

    Will a 3/8" fuel line get the job done ok? It will have a 1/4" return line.

    Any other opinions on my combination?
     
  2. 2JvLo

    2JvLo Member

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    Are you running a stock fuel pump or electric?
     
  3. FauxPontiac

    FauxPontiac New Member

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    I will run a stock pump but if I get annoyed with fuel drain back and AFB dry float bowl disease from not using it often enough, I will go to an electric pump. The only electric pump I have experience with is the Holley Red Pump. What I dislike about those is they are annoyingly loud and the bottom plate corrodes due to ethanol in the fuel. So to answer your question with a question, what electric pump would work well, and how does mechanical vs electric affect fuel line size?
     
  4. Cadillac Kid 1

    Cadillac Kid 1 Well-Known Member

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    If you have no plans for a bigger motor 3/8 inch is satisfactory.
    Greg Surfas
     
  5. Darius

    Darius Well-Known Member

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  6. Darius

    Darius Well-Known Member

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    Crap!! I lost the message when I went out to get these two links. CRAP!!

    Short fricking answer: 3/8 is fine until you have a performance vehicle that accelerates better than stock. At that point the limited vacuum of the stock fuel pump may not have enough suck to fight against the inertia of the fuel in the line. The weight of the gasoline wants to stay put while the car moves forward leaving the engine short of fuel just when its needed most.

    I've had good luck with the Carter/Weber/Edelbrock style pumps. They have proven reliable, quiet and affordable.

    https://www.jegs.com/i/Carter/180/P...MI9Yb1t-Sp5wIVkhh9Ch0xvwHIEAQYDiABEgKazPD_BwE


    https://www.jegs.com/i/Carter/180/P...MI9Yb1t-Sp5wIVkhh9Ch0xvwHIEAQYFCABEgJilPD_BwE

    d
     
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  7. mario

    mario Well-Known Member

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    I've used the marine version in my 56 gmc, 514 ci. For 20 years, finally gave up. I am replacing it a holley sniper f.i. with it's own fuel pump.

    Bro. D. Can attest to riding in that Jimmy. Lord knows I never could drive it like I had an egg between my shoe and accelerator pedal. By the way, i have 3/8 tubing. The pump is a pusher so it should be mounted close to the tank and low.
    Ciao,
    Mario
     
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  8. Darius

    Darius Well-Known Member

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    That ride in Bro. Mario's Jimmy was a few years ago but the experience still brings a smile to my face. :D

    Now, about him driving like there was an egg between his foot and the go pedal, I remember it being a hard flattened, fried egg! :laugh:
     
  9. mario

    mario Well-Known Member

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    Bro d:

    But It was Sunny side up, to match my personality...:laugh::laugh::laugh:
    Ciao,
    Mario
     
  10. FauxPontiac

    FauxPontiac New Member

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    Excellent replies, thank you. I had never thought about the inertia factor. I will probably go electric now that I know someone makes a less noisy pump.

    If I go with an electric and not even hook up the mechanical pump, then I don't need to order a return line? Or does the mechanical pump need to stay in play?
     
  11. kzhurley

    kzhurley Active Member

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    You will need a bypass style regulator and a return line so you don't overheat the pump by deadheading it.
     
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  12. Darius

    Darius Well-Known Member

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    With today’s benefits of the internet I ASSUMED it would seem easy to get information about a silly electric fuel pump. Think again.

    Using Google I started to research "return lines" and "fuel pressure regulators" for the two pumps noted about. It did not go well. Finally got frustrated enough to look for a Edelbrock's tech number. After waiting on hold for 11 minutes a guy came on only to tell me that the two part numbers that show up for those pumps weren't even in computer their system. Say What!!??

    Those two fuel pumps had over the years been made, or sold, by different companies: Carter, Weber and lastly Edelbrock. So why was it the Edelbrock Tech guy had nothing?? Hell if I know.
    In frustration I tried looking under Carter and low and behold they DO show those fuel pumps. Was this the place for answers? Not a chance in Hell.

    What was found was this: https://www.hotrodders.com/forum/carter-p4070-fuel-pump-how-does-not-need-fpr-423273.html

    "The Carter pump has an internal fuel bypass loop that limits the output pressure to 7 psi....and with a Holley performance carb would need no fuel pressure regulator...so that is why it is referred to as not needing a regulator."
    *******
    "For your case you have a different fuel psi specification, and would thus need to regulate pressure down to 3-3.5 psi and you would need a regulator to do that....the Carter pump won't just automatically adjust itself to the psi you need, it will happily keep pumping away to it's 7 psi limit."

    "If the Carter pump didn't have the preset 7 psi internal valve it would be able to make even more pressure, to the point of either stalling out the electric motor, going into cavitation, or shortening the life of the electric motor or pump.
    Carter does sell a higher pressure Competition pump that does need a regulator even for performance 4 barrel applications.
    All you need to do is put an inline regulator between the carb and the 4070 pump and set it to your pressure requirement and your all set, good to go, no worries."


    After WASTING MORE THAN AN HOUR the question of whether or not a return line is needed is still a mater of personal preference. And the question of an external pressure regular appears just as uncertain. Nobody knows anything and apparently nobody cares.

    Have a nice day,

    d
     
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  13. 5one9

    5one9 Active Member

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    A simple Holley deadhead regulator works well with any fuel pump less than a Holley Red pump. Any pump that is bigger really just creates heat, hence the bypass regulator. If the pump itself doesn't make more than 7psi then don't use a regulator at all unless you just want to protect against a pressure surge which might overpower a float. I recently bought the pump pictured new in box for real cheap. It is 8an in and out with an internal deadhead regulator or remove a plug and add a 8an bypass back to tank. I'll use it when I turbocharge the engine, assuming that I do a blowthrough carb system. Otherwise it will be fuel injection.

    IMG_3852.jpg
     
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