Re: {Chrysler 300} Carter AFB mystery part

I've seen this on AVS, can't remember if it's on AFB. I think it's function is to let vapor escape at idle to prevent excess pressure causing too rich a mixture. I believe when the throttle opens, linkage allows the vent to close and vapor is then 'vented' internally.

Pretty sure I've seen it on 2 bbl carbs as well.

On Tue, Aug 25, 2026 at 11:53 AM 'Andy Mikonis' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:

I am going through a pair of 2903S carbs that have been off the road about 55 years. One of them came to me already disassembled. I took apart the other one, and started shopping on Carbs Unlimited (thanks to Bill Elder’s informative article on our tech page.) I came across the “Rubber Vent” and I realized there is one of these in the loose parts of the pre-disassembled carb, I did not find one in the carb I took apart. I don’t see it in the shop manual, or in exploded diagrams of two different brands of carb kits, or on the diagram on Carbs Unlimited’s site. Is it supposed to be there? Where does it go?

It is a rubber disc about 11/16” stepped on one side with a pointed nub. Here it is on Carbs Unlimited:

G679 - Rubber Vent
carburetion.com

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