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
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
