Setting Rochester Quadrajet AV Tension
The AV is the flap the covers the secondaries of the carburetor. The AV flaps only open when the demand for more air is present (WOT). When decreasing the tension on the AV spring it allows the secondaries to open faster and allows them to open wider due to lower spring resistance against airflow.
To adjust the AV Tension you will need a small allen key and a very small flat headed screwdriver. That's all that's required.
Make sure never to turn the adjustment screw more than a 1/8 of a turn at one time. If the tension is over tightened the spring will be destroyed leaving your carburetor in pretty bad shape. The carburetor will have to be removed and a new spring purchased and installed - which is no easy task.
As long as you only make small adjustments you will be safe. Never adjust the screw more than 1 turn!
On the passenger side of the carburetor toward the rear you will see the linkage for the secondary air flap. If you look close through the slot in the air flap linkage you will see a very small screw.
Don't turn it just yet! There is an Allen key set screw positioned on the underside of the overhang on the air horn. Loosen the setscrew very carefully and just enough to allow the AV tension screw to turn. Turn the AV tension screw counter-clockwise until the AV flaps open up.
| 
