Carter Thermoquads ~ 'More General Information'

The acc pump nozzle type that is used on the CS Is also used on Carter AVS carbs used on Chry V8s. I do not think it is an anti-siphon feature [ could be wrong ], but rather a way of atomising the fuel discharging from the pump nozzles. I have only seen this type of nozzle on these Carter carbs. Edel carbs & many Carter models do not use them.

I always use a 0.039-0.040" sec HSB, if it is not already. My reasoning is that because the sec jets are so big, the more air that is pre-mixed with the fuel will improve atomisation. When you see these carbs on a dyno, or a video of one, the AV opens very quickly, maybe a second from closed to fully open. So I think the sec HSB size is not a big player in rich/lean. Rich/lean at WOT can be adjusted by the sec jet size.
Not done any experimenting with AV door opening on a dyno, but it would obviously affect distribution. This is one of the great things about the TQ: all the things that can be varied/adjusted. On a low perf engine I set them at 750-800 against the black body; 850 on a HP engine.

If you go to Fuel Systems on this forum, I started a thread recently on TQ mods. There are pics there of the sec mods. Doing that mod on a 455 Pontiac, a 143 sec jet gave perfect A/F ratio on the dyno [ 6000 production series TQ ] . On that particular carb, I straightened the bent section [ front ] of the AV; the CS AV does not have this bend, that is where I got the idea from. But no back-to-back testing done on that.