Yeah that's a problem. The only way I would do it is if the block was empty. That way you can wash it with Dawn and water and hose it slap back out with the garden hose. Yeah, it's that important. Is the only one you have the 3 stone? Any of the big box parts stores should have the little dingleberry brake cylinder hone. That's what I use. You'd have to work DAMN HARD to over hone with that. Spray some good penetrating oil (not WD40) in it and go.