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Technical Progressive vs. straight pull carb linkage

Discussion in 'Traditional Hot Rods' started by Custom Riviera, May 19, 2020.

  1. Custom Riviera
    Joined: Jan 16, 2006
    Posts: 35

    Custom Riviera
    Member

    Someone please help me understand the benefits of using a progressive carb linkage vs. a straight pull linkage?
    I'm installing a vintage Weiand intake with dual Stromberg 97's on a 59AB with a stock cam, standard bore, Edelbrock heads and tube headers.
    The Weiand intake manifold design places the carbs directly above the intake ports on the block, does this design require the use of a straight linkage pull on both carbs?
    Would a progressive linkage starve the front cylinders until everything is opened up?
    Is there any advantage to using a progressive linkage vs. straight pull on this configuration?
    Does anyone have experience with this particular intake manifold and are you running straight or progressive linkage?
    Any thoughts or suggestions are appreciated.
    Thank you, Jeff
     

    Attached Files:

  2. Most multiple carb setups had progressive linkage to allow the engine rpm to raise to increase air velocity before opening the throttle bodies. Without velocity, there is not enough vacuum to draw fuel from the float bowl. That is what caused the bog situation for a brief moment. Accelerator pump settings have a great deal to do with that. Economy while driving in normal part throttle operation is the rest of the story.
     
    loudbang likes this.
  3. That intake would work best with straight linkage.
     
  4. clem
    Joined: Dec 20, 2006
    Posts: 2,871

    clem
    Member

    Can’t see quite how the runners go, and not familiar with that particular one, but straight linkage is the only way to go, looking at top view .
    Due to each carb (probably)over each set of runners.
    Progressive linkage would starve one set or half your engine.
     
    egads likes this.
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  5. clem
    Joined: Dec 20, 2006
    Posts: 2,871

    clem
    Member

    Yes.
     
  6. clem
    Joined: Dec 20, 2006
    Posts: 2,871

    clem
    Member

    Yes
     
  7. clem
    Joined: Dec 20, 2006
    Posts: 2,871

    clem
    Member

    No. Don’t even consider it.
     
    egads and 31Vicky with a hemi like this.
  8. clem
    Joined: Dec 20, 2006
    Posts: 2,871

    clem
    Member

    From what I know ;
    Progressive on a Y manifold, or a triple carb manifold with correct runners, to evenly distribute air/fuel mixture to all cylinders.
    For two carb manifold , straight linkage ,smaller jets etc to fine tune.
     
    egads likes this.
  9. Rand Man
    Joined: Aug 23, 2004
    Posts: 3,480

    Rand Man
    Member

    For a dual four barrel setup, always use a straight linkage. I have a 3x2 intake with a straight linkage. If I stomp on the throttle, it spews gas up and covers the windshield. I had to adopt a less aggressive style. From an engineering standpoint, the progressive linkage makes more sense to me.
     
  10. Joe H
    Joined: Feb 10, 2008
    Posts: 901

    Joe H
    Member

    Depends on carburetor size verse cubic inch. Twin small carbs work well with straight linkage when total cfm is in the range the engine needs. Twin big carburetors ( to much cfm ) need progressive linkage so the engine has time to come up on rpm before full open. Size the carburetors right and the engine will run better due to the mixture being evenly distributed front to back. Progressive linkage means one half could run richer till under full power due to the placement of the carburetors ( not centered on engine ).
     
  11. tubman
    Joined: May 16, 2007
    Posts: 4,994

    tubman
    ALLIANCE MEMBER

    With a manifold configured like this one (called a "Super" dual), progressive linkage WILL NOT WORK not matter what size carbs you run on it. You may be able to get it started, and it may run, but that's about all. If you live in an area where there is cooler weather, I would also worry about the lack of carburetor heating on that. Those manifolds were made mainly for racing.
     
  12. Rand Man
    Joined: Aug 23, 2004
    Posts: 3,480

    Rand Man
    Member

    Okay, my comment was concerning a 327 SBC. I didn’t know the post was specific to a flathead Ford.
     
  13. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,681

    Blues4U
    Member
    from So Cal

    I believe Chevy ran the dual quads progressive.
     
    tb33anda3rd likes this.
  14. tubman
    Joined: May 16, 2007
    Posts: 4,994

    tubman
    ALLIANCE MEMBER

    If you're dead set on running progressive dual carbs on a flathead, you need one of these with the front carb as the primary. You may be able to get it to run decent. You will have exhaust heat on the primary, and almost normal fuel distribution when running on one carb. When you kick in the secondary, fuel distribution goes from "almost normal" to "pretty bad".
    Flathead dual.jpg
    See the difference? (Also, you don't have to worry about generator brackets, non-standard belts, and, in the case of early engines, the fan. These last are the only good reasons to run one of these)
     
    Last edited: May 19, 2020
  15. Custom Riviera
    Joined: Jan 16, 2006
    Posts: 35

    Custom Riviera
    Member

    Thank you for all replies. I appreciate the input, I always get good advice from my friends here.
     
    kadillackid likes this.
  16. Warpspeed
    Joined: Nov 4, 2008
    Posts: 528

    Warpspeed
    Member

    As already said by everyone, the linkage BETWEEN the two carbs must be direct 1:1 opening.

    But you can still fit a progressive linkage between the gas pedal and both carbs, either some cunningly arranged bell crank angles if mechanical, or the usual progressive snail cam if its a cable linkage.
     
  17. 55styleliner
    Joined: May 11, 2015
    Posts: 540

    55styleliner
    Member

    I run the Offenhauser version of this manifold on my 286” Flathead with 2 250cfm big 97s. All of my spark plugs have the same nice tan color and I run straight linkage.
     
  18. tubman
    Joined: May 16, 2007
    Posts: 4,994

    tubman
    ALLIANCE MEMBER

    I can't make any judgement about what you're saying without seeing an actual picture of the set up that you are running. If the manifold is "rear-biased" like the one I showed, I am surprised at your statements. If it worked that well for you, congratulations.:)

    BTW, I was not recommending a progressive setup on this kind of manifold; I was just saying that if you want to run progressive, this type of manifold is your best bet. I would personally never try to use one of these.
     
    Last edited: May 19, 2020

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