Fuel line size...

Discussion in 'Street/strip 400/430/455' started by WQ59B, May 14, 2018.

  1. WQ59B

    WQ59B Well-Known Member

    Combed thru the forum, could not find much discussion on fuel line SIZE.

    Planning to be in the neighborhood of 550 HP on a T/A STG 2 SE 455. Have a Holley 1000 cfm carb on the shelf, considering using the McRobb mech fuel pump... but everything is open to the future engine builder's recommendation.

    I have to make my own fuel sender :
    ...what size line should I be incorporating in this home-made sender?

    The tank hole is small (the sender bolts in rather than the later lock ring) - maybe 2-in, so getting a fat pickup tube, a possible return line, plus the feed for the float in thru this space... doesn't leave a ton of room.

    I'd like to get the correct-sized 90-degree fitting I can thread into the new 'sender plate' that screws to the tank, so I can drill/thread that hole... or should I put that on the back burner for now?
    Julian likes this.
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Last edited: May 15, 2018
    Julian and sriley531 like this.
  3. sriley531

    sriley531 More Luck than Skill....

    Yep, go 1/2". I had the robbmc 1/2" pickup and robbmc 1100hp pump on my car prior to going to fuel injection (dyno'd 532hp 462ci) and they were both fantastic pieces, highly recommend them. I used 8an hose however.
    Julian likes this.
  4. carmantx

    carmantx Never Surrender

    AN -8 or 1/2"
    Just like they recommended above. We use the -8 lines from tank forward.
    Julian likes this.
  5. WQ59B

    WQ59B Well-Known Member

    Thanks for the input- it is greatly appreciated.

    The McRobb pump has a 1/8-in 'vapor return' port - this is a return line that I need to make a hole for in my homemade gas tank sender 'cap', yes?
  6. hugger

    hugger Well-Known Member

    It can return to one of the other ports on the top/side of the tank
  7. WQ59B

    WQ59B Well-Known Member

    My tank only has the sender hole, and the filler neck. Guess I could weld a bung to another spot- tank has been empty & dry for 20 years.
  8. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    Just for informational purposes, .... AN -8 hose has the same nominal ID as 1/2" hard-line which is .430" to .440". We prefer to use hard-line wherever possible in many applications throughout the majority of our builds because of the fact that the AN -8 hose end fittings that fit inside the hose neck down to roughly .390". It's only .050" (1/20"), but why not get the most for your money. This holds true for all the AN hose end fittings. The hard-line fittings have .440 nominal ID for full flow.

    britt'sStage 1 and Harlockssx like this.
  9. WQ59B

    WQ59B Well-Known Member

    Chart I found says -8 is .391, whereas a -10 is .484.

    I'd feel better with hard line, also.
  10. Robs455

    Robs455 Well-Known Member

    Installing a hardline is not an easy job, a sharp bend the game is over. A good alternative are the teflon lines, they are not as flexible like a rubber but they last longer than anything other...
    I'm replacing all the rubber fuelhoses with teflon hoses, btw I use -8AN
    sailbrd and Harlockssx like this.
  11. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    My understanding is that AN - sizing is as follows: Multiply the AN - size by 1/16" and that should equate to the corresponding Hard-Line ID.

    i.e. (AN -8)= 8/16" which is 1/2", and that should have an ID the same as a 1/2" hard line ( 1/2" OD minus .035 X 2 wall thickness nominal = .430" ID).

    Bending hard-line is actually very easy but you must have the correct quality bending and flaring equipment. I have the Uniweld 1/2" bender which is a little costly ($65.00). We are buying a new 5/8" Uniweld bender for $98.00 right now as I am moving to 5/8" hard-line for the fuel system on my Skylark.

    Contrary to what folks may think, I have found that bending thicker walled tubing is superior to maintain a consistent radius.

  12. BrianTrick

    BrianTrick Brian Trick

    AA10EBF7-4D8B-43D2-9B18-25ECADAC39F3.jpeg 5542C833-F21B-4F14-A9FB-74AE92377577.jpeg RobbMc makes two different sending units. One with AN fittings,and one without. Both 1/2”. I had Inline Tube make me a 1/2” stainless line that copies the OEM line.
    In years past,I bought a spool of aluminum 1/2” line,and bent it myself.
  13. WQ59B

    WQ59B Well-Known Member

    SS line would be great, not going to happen from a vendor for me; I'm too non-traditional. RobbMc doesn't offer a 0-30 ohm sender unit, which my fuel gauge needs, either. While I'm complaining- no exhaust or brake lines available either. WHEEE!
  14. BrianTrick

    BrianTrick Brian Trick

    What car do you have?
  15. WQ59B

    WQ59B Well-Known Member

    In the sig & the avatar : '59 Invicta.
  16. HotRodRivi

    HotRodRivi Tomahawks sighted overseas

    I know a guy who has at least 60 Invicta, le saber, all 1960. Its an amazing site to see standing atop the hill to his property. Unless you have the 425 with dual carbs 1/2 sounds too big.
  17. WQ59B

    WQ59B Well-Known Member

    Stock '59 is a 364 in the LeS, or the 401 in the other lines.
    My car is going 455 with TA Stg 2 heads.
  18. Schurkey

    Schurkey Silver Level contributor

    How much fuel can you push through two needle 'n' seat assemblies at the pressure required by the carb?

    Let's look at some Math:
    600 horsepower nicely tuned will burn about 1/2 pound of fuel per hour, per horsepower. Maybe less.
    600 / 2 = 300 pounds of fuel per hour.

    Fuel weighs "about" 6 pounds per gallon.

    300 pounds / 6 = 50 gallons per hour delivered to the carb at a suitable pressure.

    Your engine requires 50 gallons/hr at maximum power, plus whatever you return to the tank through the return part of the pressure regulator.

    With a "pusher" pump generating higher pressure, and a regulator near the carb that drops pressure to what the carb(s) can accept, I bet you can do this with 3/8 tubing (depending on how much you want to return to the tank, and the restriction of the filters.)
    StagedCat likes this.
  19. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    Update: As I was removing all my existing AN -8 braided Aeroquip line and fittings from my entire fuel system today, (because I'm installing all 5/8" Hard-Lines), I decided to measure the inside diameter of one of the Aeroquip hose end fittings. The ID measured .360" which is even smaller than I had thought. That means when using -8 hose (.430-.440 ID nominal) and installing a hose end, you actually restrict the flow down to .360" which is less than 3/8". So you end up squeezing down .070" less than the hose ID. That's a reduction of almost 5/64" (the thickness of a standard 455 compression ring).
    I'm sure various manufacturers hose ends ID could vary slightly.

    This is a perfect example of why I use Hard-Lines with full flow fittings (same ID as the line's ID) as often as possible, ..... especially for my engine oil balance lines, as it affects the volume which is its intent in the first place.

    The information herein may not have a great effect on the OP situation, but depending on your particular situations requirement this could be of great merit.

    IMG_3981.JPG IMG_3984.JPG

    Last edited: May 20, 2018
  20. Schurkey

    Schurkey Silver Level contributor

    "Hard lines" (Metal tubing, OEM-style plastic tubing, or the equivalent, is by far the best choice. Hose should only be used where needed, and the minimum amount.

    I prefer Teflon-liner hose--also called TFE- or PTFE-liner, and sold by a dozen suppliers. I tend to use Eaton/Aeroquip where it's either #2807 (single-layer stainless wire braid), #2808 (double-layer stainless wire braid, high-pressure applications like PS pressure hoses) or their "TFE Racing Hose" which, as far as I can tell, is 2807 sold to non-industrial buyers at higher prices. 2807-8 has a .420 hose ID.

    This is a -8 hose end.

    Last edited: Jun 3, 2018

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