First of, what part won't come undone? The plate or the threaded stub? If the stub is off already then do what Sedanman said. Or are you having problems getting the threaded stub off? If you are, and this design does not have an internal allen head drive then some creativity with a socket in a lath is needed. Remove the tapered portion of the leading edge of the socket so that it is flat. Once the plate has been removed, using Sedanman's method, check to make sure that the gasket that was used is just the "perimeter" style gasket and not the "3 spoke" style gasket that come in some kits. Also being that you have 75lbs oil pressure, you should be adding 4 more holes between the 4 holes that exist in the plate. They don't have to be as big, just do it!
