Dual quads versus big hammer!!!...

The reason I ask is it's demand of CFM's that pulls the back flaps open. You may not be drawing enough to pull both doors open, so both stay shut. IF you run off of just one carb, and it pulls that back flap open in a second, then that answers it.
when I disconnect the carburetors and it's idling and warm. I can blip the throttle and it smacks the rear door open on either carburetor. Those primaries are so damn small there's no way those secondaries don't come into demand. I'm not saying all of them but I'm not sure as well... One thing for sure I feel like I'm about halfway there and then feeling I got yesterday from the car finally gave me quite a relief that I was heading in the right direction.. and that direction was much leaner...