What is this square "box" for?

[spoolboy]

I haven't seen this on other images of carbs. What does this "box" do? The rear booster tube sits into it. But it's only on the passenger's side.

[novadude]

I think that was unique to Chevrolet 1965-1969 carburetors (maybe just small block?).  I believe it was added to address mixture distribution on the "high" side of the dual plane manifold.  Maybe others can provide more info.

[spoolboy]

This QJ is off of an 86 Dodge truck. I have 2 of them that are identical - 17085408.

I think I saw someone say it was a stop for the air door somewhere, but I made the door adjustable and it doesn't contact it even when fully open.

[77cruiser]

I think that was unique to Chevrolet 1965-1969 carburetors (maybe just small block?).  I believe it was added to address mixture distribution on the "high" side of the dual plane manifold.  Maybe others can provide more info.

I've heard it was about mixture distribution too but I don't know what all they were on. I've only seen 2 I think & they were on early carbs.

[novadude]

This QJ is off of an 86 Dodge truck. I have 2 of them that are identical - 17085408.

I think I saw someone say it was a stop for the air door somewhere, but I made the door adjustable and it doesn't contact it even when fully open.

Interesting.  I've only seen them on the early carbs.