I have been using an old Carter 9625 AFB on my car for several years and have finally decided to try a Rochester Quadrajet.  As is often the case, I was using the AFB because the price was right and will trying this particular Q-Jet for the same reason.  There are a number of technical advantages that the Q-Jet has over the AFB but an important one is the small primary venturis from the spread bore design.  The practical advantage is that Q-jets were installed on thousands of cars in the past decades and should still be relatively plentiful and cheap to acquire.

Upgrading to a 4bbl carb does make a large increase in performance.  Originally, the car did a 19.0 second 1/4 mile with the Carter BBS 1bbl carb, automatic transmission, and 2.93 rear gears.  Upgrading to headers, a Direct Connection high lift, short duration cam (PN 4120243), 318 valves, 340 valve springs, and some mild porting, the 1/4 mile time improved to 18.5 seconds.  Installing the AFB (jetted for a Chev 350) resulted in a best time of 17.078 seconds @  81.96 mph.

As I had already upgraded from the OEM Carter BBS one barrel carb to the AFB using an Offenhauser 4bbl intake manifold, the manifold is still suitable for the Q-Jet.  However, with the intake being drilled for a square-bore carb, an adapter will be required to make the new carb fit.  Luckily, Offenhauser and Edelbrock make adapters that allow the new carb to be a bolt-on upgrade.

At the time I installed the AFB, I was concerned about having a symmetrical fuel distribution between the front 3 cylinders and the rear 3 cylinders so I made a carburetor mounting plate for the intake manifold that turns the carb 90°.  This allows the carb's throttles shafts to be parallel to the engine rather than perpendicular as was supplied by Offenhauser.  I think Offenhauser supplied it that way to simplify the fabrication of the throttle and transmission linkages.  I had to fabricate my own throttle linkage for the new arrangement.