I'm tuning the car and have a problem with the S/E carb reading 20" of vacuum . The other 3 read 14". Engine idel around 1000. I can not lower this idle .
Any ideas ? I'm thinking of rebuilding /cleaning this carb. what a pain in the butt.

 

Does anyone have any experience with the zenith carburetor quad set up ? I can not understand this high vacuum.

 

I have not worked on quad, but twin and triple ZS carbs. You may want to do the easy first, loosen throttle linkage to all 4 carb-shafts and confirm you can move each butterfly individually. Then set idle of each with RPM trim adjustment screw. If the vac condition of three at 14" with one at 20" continues, then removal and cleaning all internal passages of the 20" carb is next. A new seal kit will eliminate some possibilities.
Hopefully by this time the gremlin has shone itself.
Rgds
David