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Technical Fuel line question

Discussion in 'The Hokey Ass Message Board' started by 31wrecker, Jan 11, 2022.

  1. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Needing some suggestions on my build. I have a flathead with 4 Stromberg 97's on it, electric fuel pump. What size gas line should I run from tank to pump then pump to block and then from block to each carb? Should I put a regulator before the block? Any help would be appreciated.

    Thanks in advance. 20220109_120441.jpg 20220105_161133.jpg
     
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  2. connielu
    Joined: Apr 21, 2019
    Posts: 167

    connielu
    Member
    1. A-D Truckers

    I would use 3/8" line, a regulator and a low pressure gauge (in the fuel block). Just me though.
     
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  3. Blake 27
    Joined: Apr 10, 2016
    Posts: 1,208

    Blake 27

    I'm not trying to be negative, but I think 4- 97s on a flathead is too much.
    On a street driven car low speed response will be almost impossible to achieve.
    There's no way to use progressive linkage and opening all four carbs at once will
    likely create problems, stumble, etc.
     
  4. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,894

    6sally6
    Member

    AWWW but it looks SOOO cool!!
    Plenty of gear and plenty of cam should 'help' !
    I would think 3/8" line from tank to the fuel log should give plenty of fuel to feed the 97's.
    6sally6
     
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  5. squirrel
    Joined: Sep 23, 2004
    Posts: 50,932

    squirrel
    Member

    For the lines that connect the block to the carbs, I'd use the size that fits on the barbs.

    5/16" will be plenty to feed the engine. But you could run a larger line from the pump to the block, to impress people.

    The regulator...that depends on the pump you have...but a high quality, low pressure regulator is a good idea with old carbs.
     
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  6. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,598

    Elcohaulic

    Better off erasing instead of removing new lines.

    I like to slide colored clear hose over 3/8" tubing.
     
    31wrecker likes this.
  7. Moriarity
    Joined: Apr 11, 2001
    Posts: 23,065

    Moriarity
    SUPER MODERATOR
    Staff Member

    I am moving this to the main board and deleting the other identical thread
     
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  8. Like Jim said,,,,,5/16 is plenty .
    Make certain you have a good regulator in there,,,,,these carbs can’t stand a lot of pressure .

    Looks very impressive ,,,,,,I hope you get it tuned well with the extra carbs .
    It can be a hassle sometimes depending on your combination,,,,there’s a lot of help on here .

    Tommy
     
  9. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,489

    ekimneirbo
    Member
    from Brooks Ky

    Here are some considerations. The way an electric fuel pump works, is that it provides flow......not pressure. Different pumps are however designed to work at certain pressures, so you need to select a pump that is designed for the pressure you need. Generally a carbureted set up will need less than 10 psi and probably close to half that. The key here is that too much pressure and it will overcome the resistance of the spring(s) seating the float needle in the carb and flood the engine. So you want a pump/system designed to provide that correct pressure.

    Next consider that the pump will run continuously.
    1. The pump will be pushing but not moving enough fuel at times because you are not using enough fuel
    OR
    2. You will allow fuel to be pumped in a circle from the fuel tank to the engine and the excess fuel will return to the fuel tank via a return line.

    Some newer systems have pumps that are designed to operate as #1. The best way however is to pump more fuel than you need and allow the excess to return to the fuel tank. This lets the pump run cooler and supply cooler fuel to the carb........but it requires a return line. (This is how I would do it)

    Next consideration is whether you are going to use a fuel pump that resides inside your fuel tank or is placed inline between the tank and the engine. I recommend an intank pump as they last a long time, are quieter, and run cooler. It's more difficult to run an intank pump but in the long run its better.

    So, the basic idea is to have a mesh filter mounted on a pump inside the tank. Then insert a large inline fuel filter in the line. You can put a pressure regulator tapped off the fuel line and returning to the fuel tank shortly before or shortly after the fuel filter. This keeps you from having to put a pressure regulator up by the engine. The main fuel line will then run forward and deadhead at your fuel block and carbs. That way you only have one line to run all the way forward and the return is tapped off under the car via the pressure regulator. Adjust the reg to maintain whatever pressure you need. I would add a pressure guage up at the fuel block so I could always see fuel pressure and tell if it stays where you set it even when accelerating hard. The guage could be mounted inside your dash just like an oil pressure guage. One last thing is to buy a name brand regulator from a known company (Summit) as there are cheap counterfeits that are made to look like the quality ones (Aeroquip etc.).
     
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  10. carbking
    Joined: Dec 20, 2008
    Posts: 3,292

    carbking
    Member

    Actually, 5/16 would be better than 3/8 (maybe even 1/4 inch from block to carburetors). The smaller diameter line promotes fuel velocity, and minimizes issues from hot fuel.

    Of course, you will lose kool points at shows from the self-anointed experts.

    Jon.
     
    vtx1800, rod1, joel and 7 others like this.
  11. No matter how it runs, it's darn purty.
     
  12. Moriarity
    Joined: Apr 11, 2001
    Posts: 23,065

    Moriarity
    SUPER MODERATOR
    Staff Member

    stromberg 97's like 2-2.5 psi max I am running an electric fuel pump and a regulator set to 2 psi on the 4 97's that are on the caddy engine in my 40. I don't know how hot your engine is or what jets you have (stock is 45) but mine ran rich until I jetted down to 41's . I know mine is not a flatty but it is typical to jet down with multiple carbs especially if they all open at once 401.JPG 403.jpg
     
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  13. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Its a fresh rebuild with new crank, pistons, rods, cam the works. Bored 60 over so should handle the carbs. Like you said it looks soooo cool. LOL
     
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  14. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Thank you. Good people on this site.
     
    Desoto291Hemi likes this.
  15. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Great information!!!! Thank you. Only thing that would make this better would be a drawing. LOL.
     
  16. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Awesome. Koolness is the eye of the beholder.
     
  17. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Great info.
     
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  18. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,105

    Mimilan
    Member

    With today's fuels which "disappear into thin air" or vapor lock, run a full length fuel line and return line back to the tank.
    Then put a pressure adjustable inline check-valve where it dumps back into the tank.
    The whole system will maintain the same pressure as the check valve adjustment and will re-circulate and not air-lock.
    Plus it look hidden [without an eyesore regulator]
     
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  19. BJR
    Joined: Mar 11, 2005
    Posts: 7,473

    BJR
    Member

    Block off the front and rear carbs. Run the 2 center carbs to run the engine, and the end carbs are dummies. Run line to all the carbs and linkage, no one will know, and wonder how you got it to run so sweet on 4 carbs.
     
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  20. Blake 27
    Joined: Apr 10, 2016
    Posts: 1,208

    Blake 27

    I agree, air velocity is necessary to insure good throttle response.
     
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  21. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,489

    ekimneirbo
    Member
    from Brooks Ky

    x1 001.jpg
     
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  22. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,925

    gimpyshotrods
    ALLIANCE MEMBER

    If that manifold does not have a balance passage, then it is effectively an individual runner manifold.

    Blocking off carburetors would mean blocking off pairs of cylinders.
     
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  23. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,925

    gimpyshotrods
    ALLIANCE MEMBER

    If memory serves, and someone correct me if I am wrong, the CFM ratings of Stromberg 2-barrels are as follows:

    81: 125cfm
    97: 155cfm
    48: 170cfm

    Four 97's puts you at 620cfm. This is about what you would need for a mild engine just under twice the displacement using a manifold with a plenum.

    If this manifold has a balance tube connecting all four carburetor bases together, then you effectively have a plenum.

    About the only way that this might work is if this is a true individual runner setup, meaning that there is no balance tube, and each barrel is not shared, as in each is connected to a single cylinder. If this is the case, you will, of course, have to tune each cylinder, and balance all eight of them against each other, at both idle, and and on the main circuit.
     
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  24. squirrel
    Joined: Sep 23, 2004
    Posts: 50,932

    squirrel
    Member

  25. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    That would work great but the way the intake is setup is the front carb runs the first two cylinders, the second card the next two cylinders and so on. At least thats the way it is explained to me.
     
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  26. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

  27. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    I received some real good advise from a gentlemen name Max Musgrove (Uncle Max's 97) who is a contributor on this site and owns a company here in Utah on how to set these up so I am hoping it turns out. Fingers crossed.
     
  28. Torana68
    Joined: Jan 28, 2008
    Posts: 1,320

    Torana68
    Member
    from Australia

    way back, people made venturi reducers that snapped in. Idea being increasing air speed if you couldnt get proper signal to multi carbs. I used them , they work, but not seen any for sale much in the last 40 years. They were a springy steel.
    Edit google says they are still around maybe nor for Strombregs but this should give you an idea. https://www.redlineauto.com.au/p-4262-redline-14-35-venturi-sleeves.aspx
     
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  29. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 8,719

    Bandit Billy
    ALLIANCE MEMBER

    My flathead is .125 over, merc cranked with a 471 blower and a trio of 97's. I tried running them together and it was a hand full at full romp but you could pass out sniffing the black exhaust at an idle. I had to go to progressive linkage to make it run, jet down the primary, add a Holley regulator to take the pressure to 2 pounds and dummy the chokes open on the 1st and 3rd carbs. I ran dual 6AN SS lines (feed and return) from the tank to the filter on the firewall, then 6 AN flex to the fuel regulator mounted on the blower, more 6 AN hard lines to the block and carbs and a low pressure gauge.
    upload_2022-1-12_14-49-40.png
    Your 4 97's on your flatty look bitchin!. Because it will matter, what air filters are you planning on running? And whatever you decide on, have them on the car when you tune it. These things are really finicky when it comes to air flow.
     
  30. 31wrecker
    Joined: Apr 27, 2021
    Posts: 32

    31wrecker
    Member

    Very interesting.
     

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