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Technical Dual Carb Vacuum Advance Ford Flathead 59A

Discussion in 'Traditional Hot Rods' started by Nick Agius, Dec 2, 2019.

  1. Nick Agius
    Joined: Jul 29, 2015
    Posts: 156

    Nick Agius

    thumbnail_IMG_3583.jpg Hi All,

    This has been spoken about on this forum before But not for a while... (2009)

    Ive got a pretty tired 59a with dual 97s on it, stock crab style distributor, Are people running vacuum advances on these style setups? I had read people were running chev advance weights and a guy named "Bubba" was making them in 2014 but have failed to find anything of late.

    The car revs up pretty nice but under load it tends to stumble.. Carbs are rebuilt distributor Has been gone through and coil is new. I have no vacuum setup on it now But have been told that even with it setup correctly it does not work with the dual carbs.


    Any help would be great!

    Thanks
     
  2. jaracer
    Joined: Oct 4, 2008
    Posts: 1,535

    jaracer
    Member

    Your distributor does have a centrifugal advance to advance the spark with engine speed. There is a vacuum brake that acts to retard the timing under load. Stumbling under load is more related to the carburetors; that is if the initial timing is correct. Do your carbs have choke plates? If they do, can you close the choke partially and see if that affects the stumble? If it does you are running lean. Do you get a good squirt from the accelerator pumps?

    "Modern" vacuum advance is really there for economy purposes. It allow the timing to be advanced further than normal under light load. It goes away when you load the engine because manifold vacuum drops.
     
  3. figure8
    Joined: Oct 4, 2006
    Posts: 92

    figure8
    Member

    you can hook your distributor up to straight manifold vacuum. Its the 8BA distributor that needs venturi vacuum and doesn't work well with multiple carbs
     
    stillrunners likes this.
  4. King ford
    Joined: Mar 18, 2013
    Posts: 1,473

    King ford
    Member
    from 08302

    Sharp car Nick!..I must agree with jaracer that your stumble is carburetor related.also I agree with his method of diagnosis, if you close the choke somewhat and your stumble goes away get a set of " number" drill bits( not bits marked with fractions of an inch!) . Determine the largest bit that will fit in your jets without forcing it, then go two drill bits larger and try it!....if it's better but not god yet go one number at a time until she's just right. This is all assuming that your getting a good " squirt " out of your accelerator pumps as Figure8 pointed out. And don't worry about going too far with drilling the jets, if need be you can solder ( sodder?) up the hole and redrill it. Keep us posted!
     
    Nick Agius likes this.

  5. OzyRodder
    Joined: Dec 11, 2012
    Posts: 301

    OzyRodder
    ALLIANCE MEMBER

    Condenser. Will rev up fine but stumble and struggle to move under load.
     
    Nick Agius likes this.
  6. alchemy
    Joined: Sep 27, 2002
    Posts: 18,032

    alchemy
    Member

    I have a '42 crab distributor that was rebuilt by Bubba on a '39 Merc engine, and two Strombergs on a Weiand intake. The vacuum brake line is hooked to the intake, right on a small port that has a tiny pull from two adjacent cylinders. It connects down low about a half inch from the block gasket.

    I've used the adjustment on the vacuum brake to tune some ping out of the engine before. Wouldn't want to run without it.
     
    Nick Agius likes this.
  7. tubman
    Joined: May 16, 2007
    Posts: 6,114

    tubman
    ALLIANCE MEMBER

    Jets are cheap. Don't drill them; get new ones. Not only are re-drilled jets not as precise as new ones, but they can cause problems down the line. I went through hell with an O/T car that someone had put re-drilled jets in. Do the subsequent owners (and yourself unless you have a good memory) and get new jets.
     
    Nick Agius and Jet96 like this.
  8. Nick Agius
    Joined: Jul 29, 2015
    Posts: 156

    Nick Agius

    Thanks everyone for the responses, Lots of useful information. Originally i was under the presumption it couldn't be used at all, But it would seem like that was with later 'Loadomatic' distributors?

    I still have some tuning to do on the car. I will also install new points & rotor this weekend, Adjust carbs and go from there.

    My next question is how to properly setup the advance brake, Does anyone have any answers to this?


    Thanks again,

    Nick
     
  9. brake1000
    Joined: Jan 10, 2009
    Posts: 53

    brake1000
    Member
    from ID

    Take a look at bubbas ignition web site, has info on how to get the advance brake set up.
     
  10. v8flat44
    Joined: Nov 13, 2017
    Posts: 1,008

    v8flat44

    Nick, guys on The Ford Barn can help too, check it out.
     
    LOU WELLS and Texas Webb like this.
  11. Nick Agius
    Joined: Jul 29, 2015
    Posts: 156

    Nick Agius



    Vaccum advance brake is sorted! Thank you all for the help!
     

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