Re: WAHOO! I bought a 1910 Edelbrock QJet!!!
It's pretty rare for a carburetor to be perfect for a given engine right out of the box. They pretty much all need to be tuned, even if they were set up by a carburetor specialist. I originally set my carburetor up with #75 mains, #46K pri. rods, #CK secondary rods, on a K hanger, and a blue power piston spring. It ran pretty well and was very smooth. Believe it or not, when I leaned out my primary main jets, the top end power of my Blazer's engine picked up big time. I really couldn't say that this is what you need to do because I don't know all of the details about your engine and I don't know how Weber tailored the internal restrictions in this Quadrajet model.
Anyhow, the best thing I can recommend is to find out exactly what jets, rods, and power piston spring are in the carburetor. A good starting point on most engines is to set up the primary jets and rods with #74 jets and #44k rods, then adjust up/down from there. Use the lightest power piston spring that won't make the engine surge under light acceleration and will also not make the engine stumble when you lay into the throttle gently. Set the APT to the lowest point that will allow the engine to cruise on the freeway without surging or pinging. Set the spring on the secondary air valve as loose as it will go but won't make the engine stumble when you mash the throttle (start with about 1/2 turn tighter than no slack and adjust up/down from there).
