Check ball in center front of AFB #4181S air horn---what does it do?

Discussion in 'Carter' started by GSGregg, Jul 25, 2013.

  1. GSGregg

    GSGregg Member

    I'm close to putting my '66 GS back on the road, and decided to go through the carb (with 460K miles, I thought new floats were a good idea and that led to a kit, etc.). I noticed something that has never been dealt with, and is not mentioned in my Buick shop manual or in the carb kit instructions (but I vaguely recall reading about it somewhere years ago, and I wish I could remember where).

    There is a check ball in a vertical passage at the front of the air horn, where most models put an air horn-to-body screw. It is loaded from below by a spring, which is held by a pressed-in retainer ring, and when unseated the ball will allow extra air from an angled drilling in the air horn above the front edge of the choke valve. This air passes through a hole in the gasket and enters a channel, cast into the body's gasket surface, which terminates at the vertical drillings for the idle passages. Above the check ball, the drilling is sealed by a 3/8" pressed-in aluminum plug.

    Under the plug (above the ball), there appears to be a balancing spring tensioned by an adjustment screw. I think what I read said that these parts were not serviced, and if there was a problem, the air horn had to be replaced! Like, What the H---

    Anyway, the carb was rebuilt in '79 (112K), '90 (283.9K) and now (453.5K); it didn't surprise me that I couldn't get aerosol spray to pass through, but when I couldn't blow 40-50 psi of air through it, I figured it's been stuck for quite a while. Is anyone familiar with what its function actually is? I'm guessing either a primary high-speed anti-enrichment bleed, or a deceleration (emissions) device to augment the Air Injection Reactor's Mixture Control Valve function.

    Good ol' California smog junk.

    GSG :beer
     
  2. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    at quick first glance i thought you mighta been talkin about the front shooter check ball/passage - but it does not sound like it .
    got a pic ?
    will check my carter book info when home - at work now .
     
  3. GSGregg

    GSGregg Member

    Hello, DEADMANSCURVE, and thanks for responding. The passage with the check ball is about 5/8" in front of the pump discharge passage; when my loaned-out camera comes back, I'll snap a few shots and get them up here.

    Since the ball's function is to pass air, and not fuel, I'm leaning toward it being a decel fuel limiter rather than anything related to improving performance. If I'm right about it not being serviced in the field, I'd like to smack the people who can't trust me to 'count the turns and screw it back in the correct amount' after soaking in today's EPA-approved 'water-and-lemon juice' parts dip.

    Pics as soon as I shoot'em. :TU:

    GSGregg
     
  4. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    checked my carter/edelbrock book quick - no real help there - pics n info were all standard carter afb/avs . and no "4181" showed up ?
    so I looked through my standard/hygrade catalog - found the 4181 listed under buick 61-67 small block and big block motors but it just listed kit n float numbers etc .
    had a leftover instruction sheet I checked over , thought I saw something but no dice .
     
  5. GSGregg

    GSGregg Member

    1966 was the first year for emissions control (in this case, 'smog pump') and only California had it. From the Buick shop manual:

    4053S.....401 A/T
    4054S.....401 M/T
    4055S.....340 A/T
    4056S.....340 M/T
    4059S.....401 A/T Calif
    4060S.....400, 401 M/T Calif
    4061S.....340 M/T Calif
    4179S.....400 M/T
    4180S.....400A/T
    4181S.....400 A/T Calif

    And, of course, whichever app's came later that the printing deadline. 400 = a 401 whose displacement has been arbitrarily reduced a la GM's edict against ever-enlarging engines. It seems they forgot all about it within a few years.

    So, here are the promised photos---Oh, No, they're not!

    Don't know why, but the first of five photos uploaded only partially, and the other four completely failed. Gotta get some sleep; I'll check it out later.

    Sorry about that!
     

    Attached Files:

  6. GSGregg

    GSGregg Member

    Trying the photos again; maybe they needed downsizing.....first time I've had to deal with that.....
    NOPE---I guess 800 x 600 is still too big; trying again.....


    Still no go at 640 x 480---what gives?
     
  7. GSGregg

    GSGregg Member

    Okay, trying again---this time I shot the pix at 640 x 480 and here goes:

    AFB decel checkball (2) 001.jpg AFB decel checkball (2) 002.jpg AFB decel checkball (2) 003.jpg AFB decel checkball (2) 004.jpg

    Ahhh.....that's more like it! I selected and uploaded them one file at a time.

    Here's my earlier description, in case it helps:

    There is a check ball in a vertical passage at the front of the air horn, where most models put an air horn-to-body screw. It is loaded from below by a spring, which is held by a pressed-in retainer ring, and when unseated the ball will allow extra air from an angled drilling in the air horn above the front edge of the choke valve. This air passes through a hole in the gasket and enters a channel, cast into the body's gasket surface, which terminates at the vertical drillings for the idle passages. Above the check ball, the drilling is sealed by a 3/8" pressed-in aluminum plug.


    Gregg
     

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