I recently acquired a Neon that has broken a timing belt. I had the head surfaced, and was cleaning the remnants of the coating from the old MLS head gasket off the block. This stuff was like baked on carbon.
I finally resorted to a Scotch Brite pad to get everything clean. I'm concerned about the fibrous junk left behind. I washed the oil drainage ports with brake cleaner and I'll flush the cooling system and change the engine oil before i install the water pump and start it up.
The next time I do this, what are you guys using when you have the block in the car and can't do a full machine shop treatment? I can't imagine anything aggressive enough to remove that junk that wouldn't leave at least a little bit behind to get circulated in a motor.