the word "overcarbed" can have different meanings. It is quite possible to be overcarbed at high vacuum and undercarbed at low vacuum; or, just the opposite. The is why the desired environment is important to consider. As an example, I own a car with a 121 CID 4 cylinder that came factory equiped with 2 500 CFM 2-barrels. Is is over carbed? The factory evidently didn't think so.
But to try to answer the question: as a general rule too large a carb (high vacuum) will cause the engine to run lean (insufficient venturi air velocity) up to a certain RPM. Too large a carb (high vacuum) will also cause sluggishness at high vacuum. Too small a carb may have excellent throttle response (up to a point), but will fall on its face at some higher RPM.
Oh, and by the way, my own Pontiac 350 sits under an 800 CFM Carter TQ (and loves it ).
Jon.
Good carburetion is fuelish hot air Owner, The Carburetor Shop LLC
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