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Thread: whats the ideal Fuel line setup for triple carbs?

  1. #1
    Registered User overdrivex's Avatar
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    Default whats the ideal Fuel line setup for triple carbs?

    from searching these the setups I have found so far.



    setup 1- filter > FPR > inline,but no return fuel line.

    setup 2- filter > FPR > inline with return fuel line(i read some where that this can go in in reverse flow too)

    setup 3- filter > FPR > 3way splitter with no return line

    setup 4- uses stock rails flow in from rail>FPR than other return line.

    which setup is best for a l28, electric pump, filter between tank and pump, filter between pump and FPR

    or if you have better suggestion on fuel line setup that i did not illustrate id like to hear it

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    Good question,
    I have chosen setup 2 now, before the car run with setup 4.
    My setup is el.fuel pump to pressure regulator to filter and setup 2.

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    '72 240Z(G) 3.2L
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    I'm running filter (Holley 100 micron), pump, regulator, filter (OEM), carbs (in line w/#2 set-up) and return.

    No issues after 25,000 miles of very hard driving.
    if a little knowledge can make you dangerous, I'm a little dangerous

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    The "best" set up is #2 because it has a return line. This keeps the gas flowing through the lines and therefore at a more steady temperature, which is normally cooler.

    The second best would be #4 - if you can get a good fuel pressure regulator between the pump and the fuel feed line.

    #3 Could also be used - "IF" you have it connected to a fuel distribution block, preceded by a good fuel pressure regulator.

    Just make sure that your return line is a size smaller than the feed - to maintain consistent pressure at the carb.'s.

    FWIW
    Carl B.

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    Registered User pit crew guy's Avatar
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    I'm closest to figure two. I have a fuel cell mounted in my trunk with two Holley filters going into a Holley elec. fuel pump, the fuel line than goes to my holley regulator mounted on my drivers side fender well. I than have two lines from my regulator , one goes to my #1 carb, the other goes to my #3 with fuel line from each going to middle carb. I have no return.

  6. #6
    Registered User overdrivex's Avatar
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    cool seems like setup 2 is the most recommended. thanks for the info. there was so many options and every one said there cars ran good. but... just because it runs doesnt means it the best setup.

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    The photos show setup 2 utilizing the original fuel rail brackets with a vacuum line and canister purge to the balance tube.

    Fixitman
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    Registered User overdrivex's Avatar
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    Quote Originally Posted by fixitman View Post
    The photos show setup 2 utilizing the original fuel rail brackets with a vacuum line and canister purge to the balance tube.

    Fixitman
    nice. i also see that you found a way to hook up the carbon filter. i was having a problem finding a way to hook up my carbon filter t the carb system. i only have two rails though.

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    Registered User overdrivex's Avatar
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    i got the carbs in. im gonna go out to the the local performance shop monday to get fuel lines and see if they have some T fittings to run setup #2. also after seeings fixitmans post im gonna try and hook up my carbon filter the way he did.
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    I would suggest #2 ish.
    Tank => filter => pump => filter => carbs => FPR => return
    Cheers,
    Brady
    72 240Z, 3 x 40DCOE18, 6-1header, 2.5" exhaust, ZX 5-speed, 4.11 R180
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    I have twin mikuni 44's in my 510. I am running a low pressure Carter electric fuel pump near the tank. Aeroquip 6 stainless line with anodized fitting. It goes from pump to a Holley low pressure regulator. From there the single line goes to a Y distribution block with a fuel pressure gauge. Then one line to each carb.

    How would I do a return in this system? Could I use the older small hard line that was the feed as the return? I am just unsure the best way to plumb it into the system.

    I like that system you have fixitman. With the fuel rail. Very clean!!! Any photos of the whole car?
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    Quote Originally Posted by five&dime View Post
    I have twin mikuni 44's in my 510. I am running a low pressure Carter electric fuel pump near the tank. Aeroquip 6 stainless line with anodized fitting. It goes from pump to a Holley low pressure regulator. From there the single line goes to a Y distribution block with a fuel pressure gauge. Then one line to each carb.

    How would I do a return in this system? Could I use the older small hard line that was the feed as the return? I am just unsure the best way to plumb it into the system.

    I like that system you have fixitman. With the fuel rail. Very clean!!! Any photos of the whole car?
    Thanks. The car isn't complete yet. Other issues have been more pressing over the last few months. But you can see about 40 photos at my Members Gallery taken during the restoration process. A few photos are seen belwo.

    Fixitman
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  13. #13
    HS30-00352, HS30-101370 240znz's Avatar
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    The NISSAN factory triple fuel rail does not have a return.

    I have run new lines anyway but will just block off the return at the frame rail so that I can run the original carbs if I get sick of the 44phh's...fat chance.
    Zed not Zee

    HS30-00352 still being rebuilt (year 6)
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    This may not be applicable but I've been running setup #3 on my road racer for 4 years now, with a return line from the fuel block and a Holley bypass regulator, Carter comp pump (100GPH), 1/2" ID fuel lines (8AN hose). I originally had twin solid-state pumps and a 6AN feed line but the fuel pressure dropped off at 7k. The return line is easier on the pump too.
    Phillip Reith
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    I am still lost as to where I plumb my return from based on my previous post^ Anyone???

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    Quote Originally Posted by five&dime View Post
    I am still lost as to where I plumb my return from based on my previous post^ Anyone???
    With your current setup I don't see how it would be possible. This will probably open a can of worms, but IMO a return line should not be used with a inlet style pressure regulator but rather a bypass style - after the carbies liks an FI setup. It creates a potential for fuel starvation at high rpms because the pump then needs to supply enough fuel for both the carbs and the return line to maintain pressure.
    Phillip Reith
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    '94 F250 Powerstroke Diesel
    '97 BMW 328IS - daily driver

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    Makes sense. So what would you recommend to resolve this and run a return? Could I replace my regulator in order to run a return line?

  18. #18
    Registered User overdrivex's Avatar
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    the guy i bought them from said i should run setup #1 with a lower pressure fuel pump and a FPR that can be set to 3psi. some sources ive found that use setup #1 say the same thing. i tried sourcing a 3rd T fuel bonjo for setup #2 with no luck . i email dellorto in UK and its gonna cost $80shipped 7-21days just for that one bonjo. that's almost half the price of one used carb. i also said i wanted to run setup #2 in the email and said it would be ideal setup. they also recommended setup#1 with a low pressure pump 3-7psi and a fpr adjustable to 3psi. i guess thats why the setup only comes with two T's cause this how they expect you to run them.
    i ask my uncle which use to be a mechanic he said a fuel injection fuel pump would put out too much pressure for a carburetor setup and would put to much stress on fuel system/line. he also said return line is important because it keeps fuel moving and doesnt allow the fuel to get to hot when it pools in the reservoir.
    so now im considering running setup one to save 80bux and in hopes to not have to wait 7-21 business days just to get the car running. and on top of that even the manufacture recommends setup #1

    just to be clear its a throw between ideal setup and recommended setup from manufacture..
    Last edited by overdrivex; 04-07-2009 at 02:20 AM.

  19. #19
    Registered User overdrivex's Avatar
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    since i wont have a return would this FPR work for me?
    http://cgi.ebay.com/ebaymotors/Megan...Q5fAccessories

    it say feul injection only but seems like all of the FPR i find say FI only.

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    Nope, that won't work. I doubt that you could get accurate adjustability at the low pressure you need.

    Also, that is for a return type system.
    Cheers,
    Brady
    72 240Z, 3 x 40DCOE18, 6-1header, 2.5" exhaust, ZX 5-speed, 4.11 R180
    83 Audi urQuattro
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    91 Audi 200 quattro Avant

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    Cheers,
    Brady
    72 240Z, 3 x 40DCOE18, 6-1header, 2.5" exhaust, ZX 5-speed, 4.11 R180
    83 Audi urQuattro
    86 Audi 4000S quattro
    91 Audi 200 quattro Avant

  22. #22
    Registered User overdrivex's Avatar
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    Quote Originally Posted by bradyzq View Post
    you know i forgot all about summitracing lol thnx

  23. #23
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    i wanted to run a pressure gauge in line since the holly doesnt have one already. i gues the best place to put the guage would be right before the last carb inline to insure that im getting 3psi to the last carb too?
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    Quote Originally Posted by bradyzq View Post
    Some things don't change - thank goodness.

    That is the same Fuel Pressure Regulator that BRE ran on the Baja Z in 1973. The original was still on the car, and you can still buy rebuild kits for it. Both the High Pressure and Low Pressure versions are identical in construction - the only difference is the spring used. The rebuild kit comes with both springs and can be used for both High and Low pressure regulators.

    Just to be safe, I rebuilt mine - put a fuel pressure gauge on it and it is right on the money.

    FWIW,
    Carl B.

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    Have to wade in here with some personal experience with triples and fuel pumps and regs.

    First piece of advice on return style regulators. Read the spec sheet!!

    I put in a new Mallory fuel pump and that Holley 12-804 reg and all was fine; For a while. Pump was a little noisy, but tolerable. One day about 25 hours of run time, the pump just plain quit. Took it out, and on the bench it would run for a while, then quit. Let it sit, try again, same thing; run, not run, run, not run, pumping water into and out of a bucket. Okay, must have burned it up. What's next....

    "I'm gonna do it right" (famous last words) I went out and bought a Mallory 4309 return style reg (1-4 PSI), plumbed it with with 6AN hose all the way to tank. I welded AN fittings on the tank outlet, and return lines, even used the front vent tube instead of the intended return line tube, as its diameter is about the same as the outlet tube, about 1/4-5/16" IIRC.

    It ran, but could not get the pressure to stabilize. Try all kinds of things. The pressure would stay up, then over about 15 minutes, it would fade off to nothing, stranding me! Sit for a while, fires back up, just make it home before it dies again. NOW WHAT!!! ArRRRGGGG!

    Finally read the instructions. (imagine that).

    "Mininum 3/8 ID hose (8AN) to and from the tank for pumps upto 100 GPH, 1/2 hose above that!!!!".

    No way what I had was going to work with the smaller than 3/8 ID tubes at the tank, no matter what size hose you want to use. Choke!

    With nothing that "worked", I stuck a mechanical style pump back on the head so I can get around until I figured out what's going on. Well I'll be damned if that car didn't run like a champ, and QUIET, at any throttle setting you wish to push to. I am still running that stock mechanical pump... Have nice stainless AN stuff going into to those 1/8NPT fittings on that pump too. Real purdy...

    Did I mention I have triple 44 Mikunis and 3.1 stroker to feed?

    Oh, and I have a really nice Mallory fuel pump and return style reg for sale if any one needs one... Its' going real cheap....


    Jim


    PS. Did this last spring just before a car show. I get there and start talking to a buddy from out of town about my whoas trying to get to the show.
    Wouldn't you know, he tells me almost the identical story about his efforts to get a fuel system to work. I ain't alone....

  26. #26
    Registered User overdrivex's Avatar
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    my heads dont have a spot for mechanical pump. would put the n47 head i have on but i know for a fact that the longblock in the car works great. while he longblock with the n47 are questionable. but none the less im going with dellorto manufactures recommendation. since im in houston i might see about getting a booster pump because of the hot humid conditions here. but... im going to wait and see if its even a issue before i start adding unnecessary items.

  27. #27
    Registered User overdrivex's Avatar
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    figured i use the old fuel rails as my vacuum lines for my carbs/manifold/and carbon filter setup.

    mabe fixitman can chime in on this question. what did you hook the purge line on the carbon filter to in your carb setup?
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