Rusted Plate In Head

In the 304 v 8. Frost plugs are used out. If u look in Frost plug hole there's a Plate of steal
In head that has hole rusted through it is it a problem for water flow or temperature control. Bought used to rebuild

 

Not sure I understand what you are looking at. Here's the core plugs in my 304.

 

In side water jacket behind frost plugs

 

I'm gonna throw out a possibility. An old steel core plug got tapped into the head and left there.

Another option could be pieces of a small block heater, but being in the head doesn't make that much of a reality.

To my knowledge, there shouldn't be anything in there, so, if possible, it should be removed.