Don't get brake cleaner on plastic.
Some plastics... it will literally shatter them in slow motion right in front of your eyes. I learned this while prepping an airsoft gun for paint. It was horrible. I sprayed it on and a few seconds later all these cracks formed all over and it just fell apart like I hit it with a hammer.
Actually brake FLUID works great to strip old paint off plastic. I used it to clean some hideous blue paint off my 1JZ cam belt cover. Just let it sit on the paint and it peels right up. Then rinse with soap and water.
Also, when you paint the block, don't get any paint on the inside of the block or inside any other engine parts. I made that mistake once and the paint overspray inside peeled and clogged the oil pump screen and contaminated the bearings... what an expensive mess. So tape off any open areas of the block before you paint.
