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  1. #1
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    Default Fuel system design

    So my engine is well underway, so I'm thinking of my fuel system design and wondering people's opinions .
    Because my car is an original Brock I don't want to drill too many holes . My engine is a 355 stroker , vt roller with hydraulic roller cam , vn heads 750 black diamond quick fuel carb , torque power hi rise dual plane manifold. Approx 400-430 hp at the flywheel.

    I have a vn ss 90l fuel tank , so was thinking of using the standard in tank fuel pump off Efi vn ss to lift fuel to a under car surge tank. Then a pro flow mechanical fuel pump (100gph) at the engine to feed the engine.

    whats every ones opinions on that ?
    My factory lines are 3/8 ( outside diameter ) with no return line .

    should I update and install a 1/2 inch line and use the 3/8 as return with a regulator ?
    Or will the dead head line be fine without a reg ?

    When I did my torana a used a Holley black to surge tank and two Bosch 044 pumps and full half inch lines to motor then regulator to 3/8 return. But that was built ls1 . The fuel system was awesome but the buzzing of the pumps was a bit annoying. Trying to keep this one simple

  2. #2
    Part of the furniture monaroman76's Avatar
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    What's your intentions with the car? Just a Streeter I'm assuming? I personally wouldn't bother with a surge tank if that is the case, I'd just use a Walbro 255lph in tank pump or similar up to a bypass reg and add a return line. 3/8" diameter is fine.

  3. #3
    Part of the furniture monaroman76's Avatar
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    Your method will also work fine. There are plenty of different ways to go about building the fuel system, but I like to keep them simple.

  4. #4
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    I guess I want a little insurance that at wide open throttle I'm not going to get any lack of fuel. In the 90 litre fuel tank is a small swirl pot ( from factory ) .
    Car is mainly a streeter but I do love power cruise , and a bit of hill climbs , it's driven not hidden

  5. #5
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    HI
    Holley use to have a fuel flow sizing chart in 1 of there older paper manuals . [ not to be confused with fuel pump charts ] Once u are aware of flow this cabe matched to pipe size . Holley do have this when u phone them .
    Generally 450 hp is the limit of 3/8 fuel line.

    Max Fuel flow calculation
    http://www.onallcylinders.com/2013/0...ions-answered/

    This includes it all including
    supply pipe sizing
    return pipe sizing
    garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/
    Last edited by swampy; 10-12-2018 at 01:22 PM.

  6. #6
    254RWHP boat anchor EVL253's Avatar
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    you can also modify an oldsmobile mechanical fuel pump i beleive it is as can get some big output mech pumps for them
    11 second E85 bottle fed boat anchor

  7. #7
    Part of the furniture gtrboyy's Avatar
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    A small electric feeder to supply high volume mechanical.

    Can do it external rubber mounted just like vl or early vn commo.

    Think the Vk were common for heatsoak/hard starting issues when hot they'd cook fuel lines?

    Only issue I had on my vh sle was fuel surge/cavitation when accelerating if tank was nearing 1/4 mark...750dp & holley black feeding 355ci....tank sump would have easily fixed that issue.

  8. #8
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    Restricting an EFI in tank pump that might run 50-60 psi down to 6psi is a bad idea. Pump was never designed to run like that & will be working overtime.

    A mech pump will be fine with 3/8" line. 450 hp requires about 40 gph at the carb with the correct A/F ratio. You want to allow a 50% safety margin, so a pump that delivers 60 gph is ok.
    After ports that are too big, carbs that are too big are probably pumps that are too big.....
    Although a larger than reqd pump want hurt engine performance, it just works harder bypassing fuel that isn't needed...

  9. #9
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by gtrboyy View Post
    A small electric feeder to supply high volume mechanical.

    Can do it external rubber mounted just like vl or early vn commo.

    Think the Vk were common for heatsoak/hard starting issues when hot they'd cook fuel lines?

    Only issue I had on my vh sle was fuel surge/cavitation when accelerating if tank was nearing 1/4 mark...750dp & holley black feeding 355ci....tank sump would have easily fixed that issue.
    VH and then VK and VL 308/LV2 engines all had a problem with fuel evaporation
    when they got very hot .. and would then refuse to start

    Holden fixed this part way into VK (still with 308s at that stage ) with a hot fuel handling package
    by adding a low pressure in tank pump (max 7.5psi from that) on the bottom of the pickup, revised
    lines to the charcoal canister and a larger return line from the fuel vapour separator on the Quaddie inlet back to the tank.

    they also reverted to the what is known as L34 fuel pump (same psi but higher gph than standard) at the same time

    Revised wiring and safety relay in the fusebox finished that.... and so the cops stopped complaining
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  10. #10
    Part of the furniture monaroman76's Avatar
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    Quote Originally Posted by GtoGeoff View Post
    Restricting an EFI in tank pump that might run 50-60 psi down to 6psi is a bad idea. Pump was never designed to run like that & will be working overtime.

    A mech pump will be fine with 3/8" line. 450 hp requires about 40 gph at the carb with the correct A/F ratio. You want to allow a 50% safety margin, so a pump that delivers 60 gph is ok.
    After ports that are too big, carbs that are too big are probably pumps that are too big.....
    Although a larger than reqd pump want hurt engine performance, it just works harder bypassing fuel that isn't needed...
    I'm not sure where you got this idea from, but it's completely false. The pump will have a higher displacement, but won't be working "overtime", in fact, it will actually be drawing less current and running cooler.

  11. #11
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    HI
    BOTH correct
    If u dead head a system most pumps hate this and even Holley says a bypass system is best for pump longevity.
    Dead heading loads a pump excessively

    If u run a much larger pump than u need the risk of to smaller fuel supply and return lines happens a lot .
    To much recirculation of fuel can cause to much agitation foaming and aeration and heating

    Really an over supply is a waste and potentially cause problems


    The only thing bad about having a high performance mech pump is its conductive of engine block heat . For a carb a mech pump is ok . For efi a correct sized elec pump is also ok

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    Yes Monaro, it will have higher displacement. You got that part right....

    But instead of delivering that displacement [ fuel volume ] @ 60 psi, the pump is being forced by a regulator set at 6psi to kill the pressure & reduce flow. It backs up in the pump.
    What I said was a 100% correct.

  13. #13
    Part of the furniture monaroman76's Avatar
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    Quote Originally Posted by GtoGeoff View Post
    Yes Monaro, it will have higher displacement. You got that part right....

    But instead of delivering that displacement [ fuel volume ] @ 60 psi, the pump is being forced by a regulator set at 6psi to kill the pressure & reduce flow. It backs up in the pump.
    What I said was a 100% correct.
    You realise I referred to using a bypass regulator? Nothing you have said here makes any sense.. You really should actually do some research before making statements you claim to be factual.

  14. #14
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    the in tank pump I will use is the standard vl carb v8 in tank pump . They are only a low pressure lift pump, 7 psi . This will pump into the surge tank, having the overflow pump back into the fuel tank. The mechanical pump will suck fuel from the surge. My idea is that the surge tank will always be full, leaving little chance of starvation . The mechanical pump I was looking at is a pro flow , 7 psi . im hoping I wont have to run extra lines.

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