Another first with Speedmaster heads. This one had me scratching my head

Rat Bastid said
It’s the chambers. They are as cast. You see it all the time.

Unless it’s really bad I just let the top cut of the seat cutter take it out.

If they are too bad then I use a cutter like PRH posted above.

That’s the first one I’ve ran into that my cutter set up for a 2.055 valve wouldn’t make it past the head deck surface.