Checking what possibilities of an air leak I can on my engine, I note that the oil filler tube is a very loose fit, which could cause an air leak.

I read somewhere on the forum that it could be unscrewed so one could replace the O ring at the base, if there is one.

Mine does not unscrew. There is a clip (of sorts) that locks it in place on the valve cover and I can't figure a way to release this darn thing, (short of breaking it off) so the filler tube can be removed.

All solutions appreciated.

Chuck