Sorry guys, but this isn't a Ford question. However, if anybody out there knew where to send me, I'm guessing it'd be you guys. I have a 1965 Pontiac Grand Prix. The Carter AFB that is on it has always been a mystery to me. Does anyone know a good online resource that I might turn to in order to help me adjust it? I've taken it to shops around town and all the mechanics just kinda scratch their head and suggest that I go someplace else. I need to know how to set the idle, mixture, etc, etc. Thanks guys.

 

Setting the idle mixture on an AFB is no different than any other carburetor.

Your problem is most likely worn metering system parts. There are a few pistons with springs under them that are pulled down by vacuum. As they are pulled down a tapered or stepped rod changes position in the main jets causing different fuel mixture for different load situations. This would have been a great design if it weren't for the fact that the pistons, the bores they fit into, the metering rods and the jets all wear under normal use.

If you can find the correct jets, rods and pistons to replace them, you might get it back closer to wear it needs to be, but you will still have worn metering bores. The pistons might be a little softer than the bores, so that they take most of the wear.

I don't know if this has been corrected since Edelbrock started producing these carbs. I always thought that there should be a replacable sleeve in the bores and I hope that Vic has corrected this. I also don't know if the Edelbrock parts are direct replacements for the AFB. If they are interchangable, you can probably get the parts from Edelbrock. They are easily replaced by taking out the screw on the little cover while holding your finger over the cover so that the spring doesn't shoot them out such that they fall in the engine or you lose them. You then slowly let the cover and the piston up and grab it with your other hand. Then you will see the main jet down in the well. Replace the jet with the same size jet, and the metering rod with the same rod and the pistons I think are all the same.

Also grab the throttle shafts and give them a shake. If they are loose, then you have a bigger problem because as I recall the throttle shafts go directly into the main body of the carb rather than a replacable throttle plate like a Holley. If there is lots of play in the throttle shafts, the carb may not be worth rebuilding. If you have a good carburetor shop in your area, they might be able to rebush the throttle shaft bores. If it takes all this work, you are rapidly approaching the point where you would be better served to find a new carb.

Hope this all helps,
Doc
ASE Master

 

Edelbrock parts are a direct replacement for the AFB's. Actually Weber carbs rededigned some of the internals before Edelbrock took over. You can usually see a W casted into the top on the later model AFB's. I don't know exactly what was done by Weber though.