Interesting stuff. Seems like I recall the annular boosters on the AV2 loose about 50 cfm against the regular boosters like a AFB. At some point of performance you will notice that, but that will never show up on a stock 350. IRC, some guys pull the boosters on the AVS2 and put regular booster in them? The AVS2 is popular for the 68 to 71 Mopar’s that ran the original AVS. I have a tunnel ram combo I am working on I was thinking about using an original Carter AVS carb, probably not a AVS2.
Our experience has been you can take about any aftermarket 600 cfm carb to replace a 2 bbl and you will be blown away by the power increase and probably run just fine, improvement over and old used 2 bbl in pretty much every direction. It is only after a year or two and run some fuel thru the new carbs and all the poorly mfg’s parts inside the carb comes unraveled you realized what the expert carb guys where taking about.
But you do not always get that lucky. We have a nearly new Holley 750 Ultra that we bought cheap because it wouldn’t it run right on a friend’s 383 SBC 430HP engine. Speedway motors shop in Lincoln,NE worked on it, even had it on the dyno, eventually said it was “too big”. The guy just thru money at stuff and hires projects out. So he switched to a smaller Holley street avenger, it didn’t run right. Then he put a FI tech system on it. That didn’t work for him either. LOL…He ended up with a qjet on it! Another friend bought the basically new $800 Holley 750 ultra for $200. His q jet on his 455 was running terribly rich. So we helped him try the Holley. Basically new yet, it ran like total crap. Took it apart and had huge jets in it like it was an 850, jetted into the 80s.. Appeared the previous tuner was trying to mask a problem it had. We spend a good part of the day messing with the ultra and never could get it to run very well, seemed like it was missing 50 HP. Out of desperation we took the top off the qjet and Jet’s upgrade, the adjustment screw holding the primary metering rods had cam undone. Tightened that up, and pulled the ultra off and put the jet qjet back on, it felt like we gained 50 HP. Still have no idea what is wrong with the 750 Ultra. I was able to tune it so it at least runs well cruising. Full throttle though that new carb still has something very wrong.