[kwmech]

If your 396 is anything like mine--after 10-15 minutes of running it is up to temp with the thermostat open and water flowing. So I think that would make the so called icing problem void. Good grief it's only high 40s out? Nowhere close to icing up in September. I'd be looking at fuel delivery, especially with that pinched/creased fuel at the bowl of the q-jet there. Check the rubber lines back to the tank. Maybe you just have a dirty filter inside the inlet. The clutch in and out makes no sense what so ever either than engine load which would come back to fuel delivery. Double check the points also. They may have closed up since last winter