MopaR&D
Nerd Member
Maybe I'm off here a little but every time I got back a block from the machine shop, I always washed them out with soap and water and gave them a good rinse with clean water and blow air dry. Clean out openings with special brushes. Can't always blame the machine shop. That a good reason to "Hot Tank" your blocks before assembling. Never can be to clean.
I also do that with blocks and pretty much any mechanical part I get whether new or rebuilt, especially something meant to go inside an engine or transmission.