Dick, I know you are among the experts on engine topics, so no challenges from me. I have heard about this concern before, but fortunately it's never happened to me. I use Dubro fuel valves on all of my airplanes and never had a problem, gas included. Now watch one bite me in the buttocks...... I guess this topic is like the one on CA hinges. Guys use them for years without a problem and then one day it gets them. Same with stock fuel tanks. I guess I have read enough about concerns over fuel valves to begin changing over to fuel dots as I go. Sold!