Classic/Antique Car Repair: Carburator issue, combustion chambers, vacuum leak

Question
I have a 1966 Ford Mustang with an autolite 1100.  The issue I am having is when I turn off the ignition the car sputters a few times before it shuts off.

Answer
The most common cause of this is the idle speed set too high. This allows the throttle plate to be open a bit too far and when the ignition is cut off to stop the engine a little too much air and fuel is drawn in as the engine slows to a stop. This fuel and air hits the hot combustion chambers and causes combustion or dieseling. Depending which engine and transmission you have the idle speed ranges between 500 RPM and and 675 RPM. The second cause could be a slight vacuum leak somewhere in the intake system. If you let me know which engine transmission package that you have I can give you the correct idle speed setting.