Do a search on it. There is alot of info. I did the other day and found several way to plug them from, sticking sparkplugs in there and breaking off the creamic to the thermactor plugs to cutting the ends off of the metal block that covers the holes in the heads and flipping them over. The last is what I did just because of the carbon build up and I have no thread cheaser to clean them out, plus my stock heads are temp.