Magnum Head / sunk exhaust valve

Hi Guys,

damaged one head while Opening up pushrod pinch, got another used one to complete….i removed the valves and found all exhaust valves totally sunk….what does cause this??

I notice this heads iron is much more softer than the other head i did….and it´s far better casting Quality (too bad that every seat is cracked and the seats are so deep)….

use it or scrap it? Budget build….i´ve used heads with cracked seats before, just did not see such deep seats before.

Thanks Michael