Strange choke question

[Frank400]

Ok, this might seem like a strange question, but here it goes.

   I know Quadrajets quite a bit, built scores of them thru the years, buy all my parts from Cliff (best parts by the way), but there was always this little mystery in the back of my mind.

    When the choke flap is closed (and or very slightly open), I was always told that the carb runs richer because there is less air available to the engine.  But isn't the slight opening in the choke tower much larger than the slight throttle opening plus the idle air bypass holes combined ??  If so, it possibly can't starve the engine from air because the throttle opening plus the idle air bypass is a smaller restriction. 

  Now here's what I think, and would like either confirmation and or opinion on.  I think that when the choke flap is closed or partially opened, the running engine creates a significant amount of vacuum in between the throttle plates and the choke flap, thus sucking exta fuel thru any orifice in there, that is the primary boosters, as well as the lower idle air bleed, thus creating more fuel thus explaining the richer mixture.....

    Is that possible ?

[quadrajam]

Sounds good to me. I've seen several other explanations using terms like atmospheric
pressure and less posative pressure Bla Bla Bla But I like your description better.

[Shiny]

That's an interesting question and I hope someone with knowledge has an answer.

I can speculate, though, that if the choke flap wasn't restricting airflow, it would not be capable of generating vacuum sufficient to pull more fuel through the airbleeds.  I don't think you can generate a pressure drop without restricting airflow.  Just my guess.

And when the choke flap is closed, isn't the idle speed increased by opening the throttle blade?  Only my speculation again, but that idle speed increase would pull more air past the choke flap and cause a larger pressure drop above the throttle blade.