How do I clean my block ?

YES, it is EXTREMELY caustic to aluminum... It pretty well ruins any aluminum it touches, especially if is nice finished aluminum . I'm a master of "learnin' it the hard way", its become a theme.

 

I second brake cleaner for the nooks and crannies.
As for the bulk of the block try some oven cleaner- I haven't personally tried it but have heard good things. Just make sure to wash it off after.

 

Ok I use a big GI trash can with hot water and tide. I use my cherry picker to raise and lower the block into the trash can. Rinse it with hot water , from my washer hookup, and dry it with compressed air. You can use long brushes to clean out galleys. I once built a fire under the trash can. Carlg

 

After I got my block back from the machine shop, I spent some time with a straightened coat hanger plunging and scraping the water jacket trying to loosen any scale and crud the machine shop hot tank didn't break loose. Then I tapped all the holes. A trip to the car wash was next, couldn't believe how much crap came out of the water jackets, core sand, rust, junk. Back home, blow it out and wipe down with Blaster penetrating oil for assembly that weekend.