[TR] SU H6 float question

[KingsCreekTrees at aol.com]

Hi all;
 
My TR3A has had a running problem for a long time that I have not had time  
to address. Finally, I am getting around to spending a few minutes here and 
 there on it.
 
After I drive it for 10/15 minutes, there is a very sudden loss of engine  
power and hesitation in the engine. I can usually maintain momentum for a 
couple  of minutes and then the engine dies. Five minutes later, it starts 
fine. I've  replaced everything ignition related, as well as fuel filter.
 
I drove the car a couple of weeks ago. As soon as the engine lost power, I  
pulled over and removed the top of the float bowls. The float in the front 
carb  was floating. The float in the rear carb  was not, and there was no 
fuel in  the bowl. There do not appear to be any external leaks in the carbs.
 
Am I safe to assume this is a float valve problem?
 
Tim