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Overall, my 350 runs great, with one exception. After reaching operating temperature (about 25 - 30 minutes of normal driving) when stopped and idling, the carb starts loading up. I searched the forums and found a really old post (Nov. 2002) by Lars "Q-Jet Problems and Tips".
"Incorrectly adjusted idle vent
Results in: Engine stalling/flooding when hot idling.
Comments: The idle vent valve is to be adjusted so that the vent is cracked open when the throttle is at idle, and it should close when the throttle is moved off-idle. If the vent does not open at all at idle, the engine may display poor hot idle characteristics and stalling when hot. If the valve is adjusted so it never closes at cruise, dirt and debris can enter the float bowl."
This describes my problem but, I can't find any information about how to adjust the idle vent valve. Can anybody help, please?
From: At my Bar drinking and wrenching in Lafayette Colorado
The idle vent valve was used from 1966 through early '70. Your '72 does not have an idle vent valve, and just vents the bowl through the normal bowl vent tube.
1966 - early '70 Idle vent:
Correctly adjusted at idle, with the vent cracked open. Adjust by bending the wire:
It's more likely that you have slight seepage past your needle/seat. At running rpm, this seepage is irrelevant. But at low-fuel demand conditions (such as idle), the seepage can exceed the fuel usage of the engine, resulting in a gradual "creep" in fuel level in the bowl, until flooding starts to occur. I would pull the needle out of the seat, blow the seat out real well, clean the needle, and then check/re-set the float level to .300".
Lars
The idle vent valve was used from 1966 through early '70. Your '72 does not have an idle vent valve, and just vents the bowl through the normal bowl vent tube.
1966 - early '70 Idle vent:
Correctly adjusted at idle, with the vent cracked open. Adjust by bending the wire:
It's more likely that you have slight seepage past your needle/seat. At running rpm, this seepage is irrelevant. But at low-fuel demand conditions (such as idle), the seepage can exceed the fuel usage of the engine, resulting in a gradual "creep" in fuel level in the bowl, until flooding starts to occur. I would pull the needle out of the seat, blow the seat out real well, clean the needle, and the check/re-set the float level to .300".
Lars
A bad float will also cause the same problem... Replace it with NAPA 2-440 if you have a 1972 Q-Jet.
Lars
I actually have that NAPA float sitting on the shelf, along with a NAPA carb kit. Thank you again.I believe that I can replace those items by just removing the air horn and leaving the carb on the engine. Correct?
Last edited by sunflower 1972; Oct 19, 2019 at 07:30 PM.
Idle Vent Valve
