A clunk cannot "make" bubbles, can it? Sure, in the first run some will bleed from a felt clunk, but man, that would be a SERIOUS restriction to cause actual cavitation!!

I HAVE, though, seen other junctions pull air INTO the system if there is a restriction in say, the vent. (Wonder how I found that out!) Try it as a diagnostic tool if you like: Plug the vent and see where air enters the line. You just might find junctions you SWORE were tight will now leak air!!!


I'm running a Wren SS with TWO FELTS in series (series tank feed) and no bubbles from the felts. Not one. Not much time on the engine but no other problems with the clunks either.