Well, the AFB is not a bad design, but the Q-Jet and AVS have some advantages over it. The advantages are mainly in the ability to tune the secondary air valve opening rate and in how the part throttle operation's fuel curve is adjusted. More finite adjustment is available in the AVS and Q-Jet than the AFB because the AFB's air valve works odd of counterweights while the other two use spring tension with the ability to adjust it. Yes they are harder to tune, but properly set up they are lower maintenance. Any of the three is better than the traditional Holley in my book. Holley's part throttle circuit is way too limited in adjustability for my taste, and I have never had one that would stay in tune.
I have had Quadrajets, Holleys and Edelbrock AFB's on my cars at one time or another, and my preference is the Quadrajet and then the AFB. I have never had an AVS, so I can't speak about them from anything more than what I have read.
The Thermoquad is not a bad idea, it's just that the phenolic resin main body causes a lot of headaches because of it's tendency to warp over time. If you can keep that from happening, it's not a bad carb. However, that is it's Achilles' Heel, and a pretty big one at that.
I have had Quadrajets, Holleys and Edelbrock AFB's on my cars at one time or another, and my preference is the Quadrajet and then the AFB. I have never had an AVS, so I can't speak about them from anything more than what I have read.
The Thermoquad is not a bad idea, it's just that the phenolic resin main body causes a lot of headaches because of it's tendency to warp over time. If you can keep that from happening, it's not a bad carb. However, that is it's Achilles' Heel, and a pretty big one at that.