Heat soak also applies to a running engine. If the carb were to be mounted without a spacer, the fuel will get hot, and vaporize too readily, causing premature detonation. (dieseling) This would cause loss of power, and consistant dead sticks. I would think the pump would become less efficient, also due to the density change in the heated fuel. My opinion here, I could be wrong, maybe 195 degrees is not enough to affect the fuel this severely, but I bet it would definately be noticeable.