You called it "square bore". If by that you mean primary and secondary throttle bores are 1 11/16", then it's from a 440. If the primaries are 1 7/16" and 1 11/16" secondaries, then it's from a 383 or 340. If it has a single air bleed adjustment with left hand threads on the front center it's from a '68. If it has two mixture adj it's '69-71. If it has a idle vent valve on top of the air horn behind the throttle pump and operated by the same linkage, it's a '68-69. If the idle vent valve is internal on the pass side, with a control arm hanging out and a 3/8" vacuum tube (hanging down at a angle) for the vacuum canister, then it's '70-71. The vacuum unit on the left side front is the "vacuum brake" used to pull the choke open when you drive away without letting the engine warm up. If there is a similar unit behind it above the fuel line inlet, then the carb was on a manual trans car. This "dashpot" has no vacuum connection.
The only thing the AVS shares with a Quadrajet is the spring loaded "secondary air valve". You can adj this to open when ever you like. The AVS metering rods are lifted with low vacuum, whereas the Quad meter rods are connected to the secondary air valves and are lifted with high air flow. The popular edelbrock performer is a very, very, very cheap version of the AVS. The edelbrock has a counter weighted air valve that has to be replaced to adj (or drilled/welded to change its weight
The CFM rating is ?????
On the 440 version I have seen people say it's anywhere from 580 to 750, but they always agree the 383/340 is 100 CFM smaller. I think the small one is closer to 500.
Chevy used it in '67 on one version of the 327 and Chris-Craft with 307, 327 and 350.
I have had two different holleys and both size AVS on my 440. The Holleys gave more power, but the small AVS gave the best drivability around town.
I have a '70 1 7/16" I just rebuilt to go on a Clifford. I want to switch to a hanging gas peddle with cable before I put it on and havn't gotten around to it. I don't know if I'm too darn lazy or I just spend too much time lurking on this board.
