If I may, I would like to correct a common misconception.
I know that after hearing the plugs referred to as freeze plugs all of my
life, I assumed that the holes and plugs served only as an area for the
coolant to escape in case the block froze. My father, in his infinite
wisdom (he designed engines for one of my employer's competitors) told me
only about a year ago what the holes were actually for.
These holes are strategically placed as a method for extracting the sand
from the block after the casting process is complete.
Doug - I never knew that - Mitchell