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  1. #1

    Default How much horsepower can stock fuel lines support on a 86 Mustang GT? Are the 87-93 fu

    How much horsepower can stock fuel lines support on a 86 Mustang GT?
    Are the 87-93 fuel lines the same size as the 86?

  2. #2
    Moderator wraithracing's Avatar
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    The fuel lines are 8mm IIRC or @ 5/16". Technically that will support up to 600 HP if there are no restrictions or obstructions.

    Personally if you are running anywhere near 500 HP I would seriously consider upgrading to at least a -6 AN feed line to be safe.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

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  3. #3

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    I’ll be under 450hp.

  4. #4
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    I made 540/618 RWHP/RWTQ on the stock fuel rails & lines with my 2004 Lightning and they were 5/16". That's a supercharged setup too which takes a lot more fuel than a N/A motor at the same power level. With a good pump 500 N/A HP shouldn't be an issue.

  5. #5

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    I've heard don't even bother until you are into block splitting territory.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  6. #6
    FEP Member vdubn's Avatar
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    I'm in this exact situation, where I will be pushing 550 to 600hp, and I have a 450 Lph Walbro, which by itself will be fine, but I'm concerned that the fuel lines may be a limiting factor. The tuner I am working with, didn't seem to think it would be an issue until you get closer to 800 hp, but after doing some logging, we will see. I may end up doing just what Trey suggested, running AN-6 from the tank forward, but for now am trying to stop the bleeding of money to finish the project.
    85 GT Hatchback, T-Tops. 2012 Coyote 5.0L Swap, T56 Magnum, GT550 Dept of Boost kit, with Eaton M122 SC, RAM 11" Powergrip clutch, BBK Long Tubes/OR X-Pipe, Flowmaster Axle Back, Stifflers DS Loop, and Rear X-member, AJE Tube Crossmember with AJE-Mod Mounts, 3.73 Posi 8.8, 5 lug Cobra 13" fr and 12.6" rear disc swap, 2004 Hydroboost Swap, MM SubFrame Connectors, MM Panhard Bar, MM front A-Arms, MM rear control arms, MM CC Plates, MM Coilovers w/Koni dampeners, MM Torque Arm (soon to be installed).

  7. #7
    FEP Power Member Ourobos's Avatar
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    Same size through 93.. You can upgrade to a 94/95 fuel rail, they flow better than the fox body pieces.

    On stock lines, 255lph pump I made 576 rwhp through a TKO.
    1986 CHP SSP Coupe

  8. #8
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    Pretty decent numbers for stock lines

  9. #9
    FEP Super Member erratic50's Avatar
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    The problem with Stock lines in that pump territory is the return is smaller than the feed. You get into situations where those high capacity pumps send too much fuel for the return to deal with. Now your return is dictating fuel pressure, not your regulator. Tunability problem here? You bet! How much fuel to give when fuel pressure is unknown!?

    good luck with your build!

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