Hey Matt, thanks for this great thread!! I am trying to learn the STOCK carb setup as well and this got me to go out and check my setup. I verified all the linkages and vacuum lines, put the paper clip on the front diaphragm linkage and took it for a drive, not only did it NOT move but the motor seems to decelerate when I floor it. So, I pulled the vacuum assembly and verified that it does work, blew into the port feeding the vacuum module and could hear it blowing into the carb body which I can only assume, this is where the vacuum is being drawn from (funny, my emission control repair manual does not even mention this module nor the secondary acceleration). I am at a loss as to why the secondary is not opening, everything seems to be correct. I had Kim push the throttle to the floor while I verified that the linkage IS free to move and open the secondary venturi, could it be that I am not drawing enough vacuum to open it? if so, why? it seems to drive just fine as long as I am not asking for full throttle..
One other thing, while checking the vacuum lines I pulled the throttle positioner diaphragm line and pulled vacuum on it, it does move but it does not hold vacuum at all with the linkages returning to their normal position almost immediately after drawing vacuum, again, my manual does not go into the operation of this unit only the complete circuit, is this supposed to hold vacuum and keep the linkage in position as long as vacuum is being applied?
as always, thanks for the help!!!