hex0rz
+1y
Well is it like sooty, carbon black?
Get yourself a wallscraper for home renovation or whatever. They're scrapers you use to get wallpaper off and whatnot.
There are many of things you can use to clean the crap off. I myself would either use Lacquer thinner, or a strong denatured alcohol. IF you do use this stuff, either get a fan in there for some air circulation or wear a respirator!
It should break the gasket down good enough for a good scraping!
Be careful not to put nicks or scratches, marrs, etc. in the block and head!