[C320-list] Fuel Filler Whistle?

[Warren Updike]

Jeff, this sounds similar to the Racor LG-100 in-line spill preventer:
  Installed in the fuel tank vent line, the Racor Fuel/Air Separator efficiently separates air from fuel forced into the line.  Air is vented, and all fuel is returned to the tank. 
I installed this a couple of years ago and have not had a spill yet.  It will shut the vent line if the unit becomes overloaded with fuel increasing the backpressure which causes auto nozzles to stop.  Yes, at $80, it's more than 3x the Wisalert.  However, it doesn't rely on sound (I'm slightly deaf esp. to higher freq.) and returns the separated fuel to the tank.  

I have pictures.  I should put them on the web site.  I should do a lot of things.

Warren & Pattie Updike
C320, #62, 1994, "Warr De Mar"
Frog Mortar Creek, Middle River
Chesapeake Bay