User Tag List

+ Reply to Thread
Results 1 to 11 of 11

Thread: Balancing twin idf webers

  1. #1
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Balancing twin idf webers

    Hi all after some advice on balancing twin 40 weber idf carbs on xflow prior to setting up on rolling rd.am i right in thinking to get each barrel even using synchronizer you adjust the air bypass screw? I get the lean best idle bit with idle screw procedure. Most info on net is for vw and they say to screw bypass srew right in and leave alone? Thats the confusing bit.thanks for any help guys

  2. #2
    Pole Position Decade Plus User
    Turbosport Administrator
    Miniliteman's Avatar

    Join Date
    Feb 2004
    Location
    the Netherlands
    Posts
    4,888
    Thanks
    38
    Thanked 611 Times in 558 Posts

    Re: Balancing twin idf webers

    Screw the airbypass screws all fully in and leave them alone.

  3. #3
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Balancing twin idf webers

    Quote Originally Posted by Miniliteman View Post
    Screw the airbypass screws all fully in and leave them alone.
    Cheers.so how do i get each barrel drawing same air on synchrometer?

  4. #4
    Pole Position Decade Plus User
    Turbosport Administrator
    Miniliteman's Avatar

    Join Date
    Feb 2004
    Location
    the Netherlands
    Posts
    4,888
    Thanks
    38
    Thanked 611 Times in 558 Posts

    Re: Balancing twin idf webers

    Make sure the throttle plates clear the (first) progression holes at the same time.
    If there is alot of difference in airflow between barrel on the same carb then something is not ok i.e. throttle plates might be bent. Usually this also means the mixture screws are not equally as well.
    A little difference in airflow between barrels is not a problem.

  5. #5
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Balancing twin idf webers

    The barrels on each carb are same but one carbs at 5 and other at 7 plus

  6. #6
    TURBOSPORT SPONSOR Turbosport Subscriber
    Turbosport Moderator
    Turbosport Administrator
    Graham's Avatar
    My Race Car
    My 1st Project
    Join Date
    Feb 2006
    Location
    Ely, Cambs
    Age
    56
    Posts
    25,110
    Thanks
    310
    Thanked 2,476 Times in 2,250 Posts

    Re: Balancing twin idf webers

    you need to adjust the balence screw in the linkage

  7. #7
    Racer Decade Plus User

    Join Date
    May 2012
    Location
    Camberley, Surrey
    Posts
    3,237
    Thanks
    5
    Thanked 353 Times in 339 Posts

    Re: Balancing twin idf webers

    Quote Originally Posted by Miniliteman View Post
    Make sure the throttle plates clear the (first) progression holes at the same time.
    If there is alot of difference in airflow between barrel on the same carb then something is not ok i.e. throttle plates might be bent. Usually this also means the mixture screws are not equally as well.
    A little difference in airflow between barrels is not a problem.
    In an ideal world, yes a bank of dual or triple DCOE's would all open exactly in unison and air flow would be the same which in turn would draw fuel identically from each jet but the inlets of engines are rarely the same. You may get the butterflies operating equally and together but to equalise the draw on each jet through each barrel / venturi you adjust the air bleed screw - thats its only purpose in life! You can achieve absolutely identical vacuum readings ie perfectly balanced which give rock steady idle's. As Graham says difference between bodies should first be adjusted via the linkage / connection between the bodies.

  8. #8
    Racer Decade Plus User

    Join Date
    Jan 2008
    Location
    Up the garage
    Age
    43
    Posts
    2,775
    Thanks
    218
    Thanked 179 Times in 172 Posts

    Re: Balancing twin idf webers

    Quote Originally Posted by Theyellowmex View Post
    Hi all after some advice on balancing twin 40 weber idf carbs on xflow prior to setting up on rolling rd.am i right in thinking to get each barrel even using synchronizer you adjust the air bypass screw? I get the lean best idle bit with idle screw procedure. Most info on net is for vw and they say to screw bypass srew right in and leave alone? Thats the confusing bit.thanks for any help guys
    Are they genuine Weber, or copies?

  9. #9
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Balancing twin idf webers

    Quote Originally Posted by HonkyWhiteTrash View Post
    Are they genuine Weber, or copies?
    Hi there very rare genuin italian matching numbers webers.on even rarer 1970s manifold. Not cheap chiner ones.

  10. #10
    Spanner Monkey

    Join Date
    Oct 2018
    Location
    Midlands
    Posts
    291
    Thanks
    1
    Thanked 8 Times in 7 Posts

    Re: Balancing twin idf webers

    Quote Originally Posted by katana View Post
    In an ideal world, yes a bank of dual or triple DCOE's would all open exactly in unison and air flow would be the same which in turn would draw fuel identically from each jet but the inlets of engines are rarely the same. You may get the butterflies operating equally and together but to equalise the draw on each jet through each barrel / venturi you adjust the air bleed screw - thats its only purpose in life! You can achieve absolutely identical vacuum readings ie perfectly balanced which give rock steady idle's. As Graham says difference between bodies should first be adjusted via the linkage / connection between the bodies.
    Cheers. This is the confusing bit as some say leave them alone others adjust them? I spose just bit of trial and error tho they must be there for a purpose! Just need get it soe thing like to get to the rolling rd

  11. #11
    Racer Decade Plus User

    Join Date
    May 2012
    Location
    Camberley, Surrey
    Posts
    3,237
    Thanks
    5
    Thanked 353 Times in 339 Posts

    Re: Balancing twin idf webers

    Quote Originally Posted by Theyellowmex View Post
    Cheers. This is the confusing bit as some say leave them alone others adjust them?
    Maybe advice from same people that put bike carbs on to cars, fit a 180 main jet and expect them to function correctly! All or nothing is never normally an option for anything!

+ Reply to Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts