Below is a photo of my block after spending what seemed like hours cleaning the surface by hand. It seems like there's an endless amount of crude baked on to the surface. I used a permatex gasket remover product which seemed to work wonders. With the help of razor scraper and a green scotch pad I got off everything that I could possibly get off. My question is, the surface is not as clean as it would be if someone were using a pneumatic tool with a wire brush, or if you were to send it to a machine shop. How clean is clean enough? I think I could scrape for days and still get stuff off. I've read a lot of forums across the internet that say not to mess with the piston crowns because you can cause more harm than good. Any opinions on block surface cleaning?