When you had the top off, did you see any rust brown sediment in the bottom? If so, thats rust and it will get by any filter made. The only thing that will stop it is a magnet. Rust will plug things up, cause it to flood over, run like poo etc. Not an exclusive issue to the AFB/AVS style carburetors either. Its even worse on Holley's as there are more areas for it to hide that cannot be cleaned out unless you use ultrasonic. Also, people all over the country, and out, have been having issues with vapor lock and boiling over due to the fuel containing too much alcohol which changes the vapor point of the fuel which means it boils at a lower temperature. As far as the rust issue is concerned, see if you can find whats called "cow magnets". Get them at a livestock store. They are about the size of your pinkie and are used on cattle to collect iron based objects, picked up when grazing, in their stomach. I've used these in cars and dropped them into the fuel tank in different spots dropping them though a piece of heater hose to distribute them. This will collect most of what gets into your tank from the main rust collection unit aka your gas station. If you use a normal metal cased in line fuel filter, this would be a spot to mount another magnet to catch what might want to slip by in the tank. If you have access to a friend at a tranny shop, the tranny pan magnets used on a lot of the Mopars 90's and up are about 2" od with like a 7/8 hole which your filter fitting can protrude through. Of course you can use just about anything for magnets, these are just low buck versions for me. What settings did you do the floats to? I have always gone with the competition series AFB settings which where 5/16 level and 15/16 drop. Thats what I used from back in my speed shop days since we were Carter distributors and a warranty station. For the boil over issue, some of the people have been experimenting with return lines to get the hot fuel back to the tank. One think I like to do is put a heat shield between the carb and manifold. You also may want to block off the heat crossover passage in the manifold. GM[ I know yuck!] used shields on some of their cars like the Vettes and Camaros that wok pretty darn well even now. It comprised of about an 060 or so thick aluminum shield with a thin gasket on each side. There are some other shields made which sandwich multiple layers of aluminim and gasket but these are quite prone to vacuum leaks so stay away from these. The GM unit can be had through Classic in the Camaro catalog. The one they make is for the standard flange carb. IE 4150/4160 Holley or AFB/AVS. I believe the number for it is 3969835 which is still the GM number. They, GM, used to make one for the spreadbore carbs, i.e. TQ/ Q-Jet/4165/4175 Holley. Number was 3969837. We used these shields a lot, especially on rv's with their high under hood temps and they really helped. Well, hopefully you can get your issue figured out with this and the input from your brethren. Good luck!
