I have a 440-6 mechanical set up. Intake is original cast iron. Original manifolds, no headers. Normal driving seems to cause a buildup of carbon on driver side of
motor. If you bring in the other outboard carbs after driving for a period of time
it blows out carbon. I have owned a 340 6-pack 70 T/A and had the same thing.
I have stock mufflers and also stock resonators. Stock exhaust pipes (no X pipes). I do not drive often, try to drive once per week, cruise ins, etc. I run 100% fuel (no alcohol) and I add 1 gl. aviation fuel to each tank to keep fuel fresh and also to improve octane. Any ideas?

 

Try a couple of tanks of the Chevron Techron Superme with out anything else and see if that helps solve the problem. Depending on where you are at? the petroleum industry should be changing over to the summer blend fuel.

If that does not soulve the problem.... Move the spark plug heat range up 2 ranges on that side and see if that helps...

However if none of that make a difference.... The Motor must have a puddling problem on that side of the motor, I would guess...

Just my thought's