[scottj]

Too large of a cfm rating, i.e. "over-carbing", will result in a small gain in top end at the expense of poor low speed throttle response- refering to engine speed. Over-carbing doesn't mean that the engine will run rich; it just means that overall drivability will be compromised. Rich/lean is a calibration issue. A carb of anysize, if improperly calibrated for the engine, could cause a rich (or lean) condition. A common mistake made is to install a large carb, calibrated for a racing engine, on a street/performance engine. A race-calibrated carb will run too rich at idle and low engine speeds on a mildly cammed engine.

Scott