Marvel MA-3A Mixture

[atcdork]

I searched and can’t find whether this has been discussed before:

‘46 C140 with Lycoming O-235 and MA-3A.
Bought the plane where it was based at 5000’ elevation. Now plane is based at sea level.

Because of increased air pressure the ‘new’ home airport, does the idle mixture adjustment screw (and idle speed screw) on the carb need to be adjusted? It would’ve been last set at the previous 5000’ elevation airport.

[6643]

You can check the idle mixture yourself.

To set the idle mixture you need to have the engine at operating temp, preferably after flying. Then with the mixture knob full rich stabilize at idle of 1000 RPM or less for at least 30 seconds then retard the throttle all the way to idle. Once stabilized at idle quickly pull the mixture to cut off and watch the tach. If there is no RPM rise when the engine shuts off the it is too lean. If the RPM rises more than 50 than it is too rich. Adjust the mixture screw clockwise to lean, and counter clockwise to enrich the mixture. Try for 50 RPM rise at shut off.