Can't break it loose: strongerg 81

[Logan]

I recently bought a stromberg 81 that was "rebuilt". And I ran it on my model a speedster for a little bit until some trash got in the carb. I went to break it down to clean it, and the brass plug at the bottom between the two jet brass plugs, will not break loose. I have pretty much almost mutilated it trying to get it freed up. My question is, has anybody else had this problem, and how did they get it freed up? I'm sure there is some kind of sealant on it or something, because of how stuck it is. The slot for the flat head is pretty much all boogered up now. (Didn't take much to do that with the brass). I'm pretty much at a loss at this point. I don't care to save the plug, as I have extras, I just need it out.