I have 1965 300 2 barrels, everything is stock, it run well at normal speed, but when traffic jam it start to run bad, stumble and exhaust pop, and after 5 min to run in normal speed it run good!
I look at the oil level in my differential, and I heard pressure sound when I removed the plug (positive or negative I don't know) so I look for any vent, and I don't find any!
Does it have a kind of vent on that?