Carter AVS Vent Door Rubber Gasket at top of Carb

[oldchevelle541]

Curious question.

Sitting at idle should the rubber grommet be tight to the top of the carburetor. If not tight what should gapping be ?

[John_Kunkel]

This varies with the year and emissions equipment but, for most, the gap is 1/8" at idle.

[oldchevelle541]

Thankyou John,

I don't think mine is an 1/8" maybe a 1/16". I appreciate your feedback.

[John_Kunkel]

Make sure the throttle is completely closed, with the choke full open.

[375instroke]

And why do I have a valve that lets the gas evaporate out of my carb when I park?

[John_Kunkel]

"Most carburetors today will use a movable atmospheric idle vent valve in place of the fixed external vent system. This movable valve will be held in an open position only during idle and park positions by carburetor linkage contacting the idle vent arm. Any tendency for fuel vapors to collect inside the float bowl will be vented to atmos­phere through this opening at idle and park positions. As car speed increases and throttle linkage is progressively opened, the actuating lever from the linkage will no longer contact the idle vent arm thereby allowing the idle vent valve to close. This action will now return the carburetor to the internal vent system thereby once again maintaining the same pressure on top of the fuel as entering the carburetor through the air cleaner.

It is important that the idle vent valve be closed during all periods of operation except at idle, otherwise excessive richness can be caused by the higher atmospheric pressure acting upon the fuel in the float bowl."

In later years the bowl vented to the charcoal canister, so there were no evaporative emissions.