[Fot] head gasket/block question

[don at dcphotos.com]

Amici, 
I’m just back from a great weekend racing Eagles Canyon with CVAR.
Car ran well all weekend till final race and the head gasket blew.

On the Spitfire blocks are two holes by #1 and #4
I’ve been told they were use at the foundry and they should be filled in.

My question is, other than to facilitate the blowing of head gaskets, 
why does the head gasket have a hole for them in the first place?

Thanks, 
Don