I’m posting this from my mobile so pls forgive me any typos. The throttle shaft on my AFB got stuck any time the car sat for some month so I decided to take the carb of, see whats going on and maybe rebuild it. I took the AFB apart, put the parts in a vibrating bath and cleaned up as much as I could. Getting down to the base plate and throttle shaft I found both heavily corroded, no wonder the shaft got stuck. The shaft also has a lot of pitting in the area where the corrosion on the base plate is. Please look at the pictures. Is the cavity in the top right bore factory or has this been eaten up by rust over time? I grinded out tons of - what I belive to be - sand, maybe from the casting process? The main question is: can these parts be rescued or should I get an new carb right away? The intake has rust in the corresponding area, so if that aint factory I guess I need a new intake as well. Pic #5 and 6 are from the top left bore, showing what looks like a weld spot from a former repair. BtW, the Carter is an A7A 4331S.
The hole is caused by the exhaust crossover in the intake manifold; over the years, the acids and moisture in the exhaust eat away at the carb base. As far as the cavity underneath, I'm not sure if that's a vacuum passage or what, but either way, that base is rough. I guess anything can be fixed, but if it were my carb, I'd be looking for another one.
It can be repaired if you can't find replacements... The throttle shaft bore could be drilled out and a bushing installed. The rust on the throttle shaft needs to be removed or treated so it doesn't come back. The carb should be installed with a steel heat shield/gasket. When those corrode, then the carb base begins to degrade.
I cleaned up all the corroded spots, treated them with rust converter, filled the pitted spots on the shaft with cold weld and smoothened it down after curing. Put everything back together, ran into new problem. Will post in separate thread. Haven´t put carb back on yet, will revert once done.
