Not sure how widely known this is. Thought I'd post for informational purposes.

For anyone wanting to ditch their barbed and vented oil filler cap for the earlier style that is open to atmosphere but without a hose barb; it turns out you can convert your vented one very easily without having to obtain a hard to find original non vented one. Simply pick up any 240 series cap from a local Pick n Pull (even a nice chrome one!). These are very plentiful and cheap. Remove the caps from both the 240 style and your vented style. Then, pull off the hose barb cap underneath the cover of your vented style. This will reveal the wire mesh inside used as a rudimentary filter. Make sure everything looks reasonably clean and simply install the 240 solid cover over the original filler cap internals. Turns out they fit perfectly, and now you have a passively vented early style cap! Reverse this procedure any time to revert back to the barbed cap.