I am getting a strong gasoline smell from the exhaust on my '67 122 wagon. It goes through a tank of gas rather fast as well. I don't smell any gas when the car is parked, just from the exhaust. Also, it almost always starts like a dream, except when I've been driving it, get it up to temp, and park for five minutes. It then will have a bit of trouble starting again. In this case it will usually puff white smoke for a second or too, then run fine.

Any clues? What are the first things I should look at to rememdy this?