Ok, here's one for you - on the Cylinder head - you know how there are two 19mm Freeze plugs on the front face of the head? The lower one and upper? I know when the engine filled with coolant (and if you were to hypothetically not drain the coolant first) that if you were to remove the lower of the two freeze plugs you'd get a drainage of coolant. But if you remove the upper you don't - why is that? Isn't the point of freeze plugs to be release points of pressure for if coolant freezes and expands? If there's no coolant in the top region, and behind the upper of the two freeze plugs... then why is it even there?

For that matter - what if water were poured into that top plug and then resealed?

Are only one half of the passages on the head used for coolant (the lower) and the other used for.... exhaust gasses?

I'm talking about the actual NON valve, non cylinder passageways that are inside the outer edges of the head it's self.

Hopefully someone with knowledge sees this - I need to know what's up

 

I may be completely wrong, but from what I could figure out from what you are saying maybe the top freeze plug is for pressure release for air (since you want that at the highest point), and the bottom one is meant for draining?
I have no clue just a shot in the dark.