Originally Posted by Lightning41
I have a zz4 in my 1941 ford. It was running perfect all last year. It is now back firing through the carb and exaust at idle. I have checked the counter weights and timing. It has a stock hei. The idle doesn't drop when I unplug the vacuum line? Could the vacuum advance be causing it to run bad? Help!
The vacuum advance won't change the idle speed unless it's hooked up to a manifold (not ported) vacuum source. If there's any chance the timing was changed, I'd check it w/a light to verify it's OK. If it sat long enough for the fuel to have evaporated out of the carb, there might be deposits that are plugging the jets/passages of the carb, and/or the air bleeds could be stopped up w/crud. I'd check for vacuum leaks while you're at it.