Greetings Afourians, My first post, GREAT SITE!!! I am currently rebuilding the A4 in my Catalina 27 "ISLE DOER", I found this plug in valve train area and can't figure out where it came from, looks like a oil galley plug. Hopefully pic is loaded up, plug is 1/2 inch high and 5/16 in diameter, with tapered shank.any ideas?