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  1. #1
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    Default Any Ideas -tips for running 3/8--1/2in. fuel line in a HQ

    hi
    As the title suggests any tips and how have u done it ??
    [I will be running a high volume mech pump, carby with existing 5/16 as return line ]

    Did u AN fitting thru the tank or sender ??
    Fixed hard line eg alloy or flexi hose ??
    pictures ??
    Ideas u would avoid ?

  2. #2
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by swampy View Post
    hi
    As the title suggests any tips and how have u done it ??
    [I will be running a high volume mech pump, carby with existing 5/16 as return line ]

    Did u AN fitting thru the tank or sender ??
    Fixed hard line eg alloy or flexi hose ??
    pictures ??
    Ideas u would avoid ?
    Iíve run 1/2Ē aluminium line. Welded a little sump in the bottom of the fuel tank. Iíll try and get some pics on the weekend for you.


    Sent from my iPad using Tapatalk

  3. #3
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by BasicQ View Post
    I’ve run 1/2” aluminium line. ....................


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    ditto here on the race car.. mainly coz it is easy to bend and hook up under the car.

    With the tank, I took the pickup/sender unit out, cut the factory pickup pipe out (left the small return one)
    and brazed in a new 1/2" steel pipe.. bent to be the same shape and placement as the original factory pickup.
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  4. #4
    Senior Member LXCHEV's Avatar
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    I’m also running a big mechanical pump on my SBC. To feed it, I also ran a 1/2” aluminium line. I had Brown Davis build my drop tank with an internal swirl pot and 1/2” pickup pipe that is welded in place and pops out at the rear for easy connection (I’m just using fuel hose and clamps). Still have the original pickup that is part of the sender unit, so this is just blocked off and no longer used.

    No return line for me, although that’s something I’d be interested in (purely to have circulating/cooler fuel).

    My mech pump is self regulated at 6PSI, so no reg required.

    I’d be interested to hear the details of how you’re setting up a return style fuel system.

  5. #5
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    This may sound counterintuitive. It is often said that the return should be larger {or at least the same size} as the supply.. I am not sure I believe this and I have not proven or disproved it either

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    hi

    Dead head non return systems have some negatives one of them is fuel is not circulated causing heat soak into fuel =poor fuel delivery. Problem can also be amplified when using a oversize huge capacity pump for application . ie Fuel is being worked to hard .

    Many of the USA cars use 1/4 return lines factory . So I suspect 5 /16 will be ok . Yes 3/8 return would be ideal but the factory line is still there so using that first . A mech pump should give less return at times compared to electric . Plus using pump fuel not a high flow requirement like e85 or some racing fuels . Time will tell .

    Done the fuel requirement for 400cu going 6500--600hp and I only just flow enough to require 50gal/hr 1/2in feed line . Its all about flow vs pressure loss over distance also.

    Mech pumps require free flowing suction line so 1/2 it is

    Probably use alloy tubing but have to insulate maybe when passing headers depending upon routing . Most likely finish with rubber hosing at each end . OR as many rubber hose the lot ...dunno have not decided
    Last edited by swampy; 29-05-2021 at 09:51 AM.

  7. #7
    Senior Member LXCHEV's Avatar
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    I wouldn't rubber hose the lot - that'd be way more prone to pressure drop (which is directly proportional to hose length). Especially on a suction line - it'll be trying to suck in the walls. Less of a concern in an output line.

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    Hi
    rubber hosing has more internal friction eg drag on fluid flow when compared to a steel pipe . A 100% hose install would be best in a nylon type lined hose or similar to reduce the negative effects .

    Going to only fit hard line to under body anyways if thats the direction i go .
    Specific to Hq etc
    H frame only in hard line
    rubber hose to tank
    [ if i cross from chassis to inner guard = flexing panels ] rubber hose in the engine bay ??
    [if i go along chassis rail ] fit hard line ?? [Have to insulate against header radiant heat ]

    I personally think braided hose looks a little ugly . I like the smooth look of hard line .Besides stainless braid is abrasive if rubbing against another surface . My opinion only ! Braid has its application as does hard line .
    Last edited by swampy; 29-05-2021 at 09:50 AM.

  9. #9
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by swampy View Post
    hi
    ............................

    Probably use alloy tubing but have to insulate maybe when passing headers depending upon routing . Most likely finish with rubber hosing at each end . OR as many rubber hose the lot ...dunno have not decided
    yes.. to the insulation (big problem on Commos due to lack of space and also on the clutch cable for the same problem)

    and at the carby end, I have a regulator set at 6psi (screwed on with a hard line adaptor)
    and braided hose from the regulator to the carb .. using AN dash fittings of course
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  10. #10
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by desoto30 View Post
    This may sound counterintuitive. It is often said that the return should be larger {or at least the same size} as the supply.. I am not sure I believe this and I have not proven or disproved it either
    For the return reg: if your input is say 16psi and you want 6psi at the carby it will allow 6psi to build between the needle & seat and reg and bleed excess back to the tank. The return is the key to regulation. Psi setting is how much is sent to the return line. If the return is not big enough to allow this to happen freely then there could be fluctuations in pressure. Return canít be too big.


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  11. #11
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    hi
    first try with 5/16 return if it work great if it doesn`t just run another line . Fuel pressure should be telling .

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    I am using a Mallory bypass reg & the instructions noted that better pressure regulation is achieved with a larger return line. I used 3/8" feed, 1/2" return. The return line must be free of any restriction or back pressure to ensure trouble free operation.

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    Hi
    GTO ,assuming u are using an electric pump??
    There is a difference between mech and electric . The mech pump regulates output to engine speed vs electric pump is a fixed delivery with oversupply occurring for majority of the rpm range. Think idling/low eng speed with high flow elec pump ,most gets returned to tank.

    Mech pump return lines Factory GM use 1/4 inch [return ] and 3/8 [supply] on 400--450hp
    For more perf above this the sizes need to increase for mech pump

  14. #14
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    I'm using a 1/2" aluminium tubing with -8AN braided hose for supply and return. Aeromotive 340 fuel pump, fuel log and FPR.

  15. #15
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    I haven't got any pics but on mine there is a flat section on the tank right next to where the sender goes in. I used a -8 bulkhead and attached a length of 1/2" alloy line to it and mounted it from inside the tank (bulkhead nut outside) and sealed it with stat-o-seals (aluminium washer with o-ring fixed in centre). The alloy tube is connected to the bulkhead with a flare and a tube nut. It's mounted into the lowest part of the flat section, which you can access the back of through the sender hole. I made an adapter for the pipe to take an EFI style screen. I have 3/8" feed and return lines under the car but I used the 1/2" in the tank to allow for any future upgrades. I'm just using the original 5/16" pick up as the return at the tank. 1/2 pick up to 3/8" line to reg, 3/8 line from reg connected to 5/16 pick up. The 5/16" pick up has enough flow for my Carter black pump as the pressure is rock steady at idle.

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