You cannot determine a jet change based on the smell from the exhaust at idle.
The main jets have very little/ nothing to do with this. Thats how you blow up engines.
I suggest you go back to the richer primary jetting for testing You want to start rich @ WOT.
The plugs fouled from the ignition fault, not the jetting.
The main jets do not effect the idle. And you cannot smell a "rich" AFR. What you were smelling was unburned fuel in the exhaust. (spark misfire, late timing at idle)
You do not want to test under boost with a main jet that is too lean @ WOT.
The 72's are big but a good safe spot to start testing with.
The carbs idle circuit may need work. fine tuning the idle feed restrictions and idle air bleeds.
Thats why they make and sell "blower carbs". cause they are set up for a blower motor.
The main jets do not come into play until you are well into the throttle. Anything below that is the idle /off idle circuit.
The power valves must stay closed at idle to idle clean too.
Last edited by F-BIRD'88; 01-22-2013 at 02:45 PM.