Fred, Scott's got a great point.
If you're going to relocate the tube anyway, you can get a drain plug at any plumbing supply house. I have a brass plug in the bottom of my breather tank; it's a keeper for a hole I'll use to dump to the exhaust.
In your case, having the tube drilled and tapped for an upward departure means you'll have to remove the filler neck anyway, so checking the plate is something to do at that time.
There's an old plug in the back of the filler neck on my car, about 3/8", where there used to be a drain line. It came from an external source, apparently, and has not been in use since I bought the engine. I was thinking of using it for the same purpose as you -- but I got talked out of it.
The origin of the oil that drips out of that tube is the spinney-around parts right underneath that filler neck. That's why the defelctor plate is there.
While there's pressure in the case, there will always be oil flung up into that deflector plate. It will always spray oil upward through it and into the filler neck, so putting a breather there will always result in oil-laden vapors trying to get somewhere where there's less pressure.
Which is also -- apparently -- why some folks vent their through their valve covers to an external tank above the highest point on their engines. In theory, the oil doesn't creep up the tubes and spit out the first hole it comes to; instead, gravity keeps the liquid oil to a minimum and it's the vapors that go into the tank or carbs, wherever. That's the route I took, but some people here have those lines running to their carb covers instead, using the draw of the carbs to pull the pressure out of the case. That vapor has to go somewhere ...
Does that help? It mostly works for the Hoopty, but there's always a little liquid oil in the tank at the end of a long day.
