Ive never had boiling fuel in the lines. mine has a fuel retun line so the gas cools down. how hot does the engine run? Ive always kept it at 160. Even on a hot drive; the temp goes to 180 to 190. that boiling can cause a vapor lock in the carb. rodchester carbs are a pain to deal with. sometimes the screws on the underside will loosen up and that would cause a gas leak which would drive you crazy because you do everything right and still smells rich. to test for this, you wiggle the carb while its on the engine and bolted down. if it moves slightly then the 3 screws are loose. remove it and tighten them down. this could be the cure for you.