Was cleaning this AVS, blowing it off with 50psi, and this check ball appeared. I don't know if it was stuck, and I broke it loose, or if I blew it around to the other side of the spring. Sounds crazy, but I'm sure the ball should be on the other side of the spring being pushed up against the off idle mixture screw. Anyone know if this is messed up or not?

That is a pressure relief valve to allow any pressure in the float bowl area to escape form the carb. instead of forcing fuel out of the carb. some way else

There's a half inch hole on top of the carb for that. This leads to the idle passages in the venturis.

Here is a pic I have on some of the idle circuit on the AVS/AFB. Looks like that may be going to the an idle air bleed ? But I am not sure by this pic as it really don't show that and it looks like the air bleeds are in the booster unit and not the top housing ? But you said it goes to the idle circuit then it sure sounds like its for the idle air bled ? Ron

the ball should be at the top of the housing with a spring under it. it's my understanding that it opens at high vacuum (like deceleration) to let air in the primary circuit. an emissions thing but doesn't seem to have an adverse effect on driving.

That should be correct.

Kinda reminds me of the Decell valve that I saw on some Fords when I worked at a Ford dealer years ago. It would open under high vacuum on decell and pull extra air into the intake to lean it out some on them conditions. It was for emissions also. It makes sense that it works that way. I just have never seen it before and I thought I have seen most everything on an AVS ? We learn something everyday. Ron

that little check/ball valve actually helps eliminate some exhaust stink. I found this out by blocking it once. seems to have little to no effect on idle and cruise.

Being that the check ball is on the bottom with the spring above it makes me think it will not be suck open, it has to be forced up to open

i think it's missing the spring, or it got bubba'd.

The ball is above the spring !

Yea looks like on high decell vacuum it pulls the ball down a tad and pulls air into the idle circuit. It seems to just open an idle air bleed I guess on decell at high vacuum to lean the idle some on decell ? The top of the carb reminds me of the Quadrajet that had the feedback setup in them. They had a solenoid in the bowl under the airhorn that looked like that with two holes cast in the airhorn as the solenoid would cycle to control the fuel mixture at idle by opening and closing the idle air bleed. The solenoid also hooked to the primary metering rods to control fuel mixture at part and wide open throttle. Ron

Where did the notes about this valve come from? Carter course notes?

Thanks for that drawing, 62maxwgn. So it looks like I should try and pull the bottom orifice plug out to put the ball bearing against the adjustment screw. I found a pic of another AVS, and the ball bearing is not visible through the orifice.