The four-head-bolt-holes-per-cylinder bore on the block are blind, which means they are closed off at the end. For this reason, it is critical you get all fluid or solid material out of these holes before torquing down the head bolts. Most engine shops use dry, compressed air to blow the holes out (shown) and sometimes brake cleaner to loosen up any material in the holes before blowing them out. If you torque down the bolts without doing this, there is a good chance the block will crack, making it junk.
Gen III GM Small Block Tech