My home inspection of Speedmaster heads

You have two options as to why you have bald spots in a port.

Tool defection or the casting is big there already.

Snap gauges aren't my favorite tools, especially in places with compound curves, but I've been able to get repeat numbers that confirm the section missed by the CNC is because the casting was already big enough.

I'm seeing a .010-.020 difference, but that's within the margin of error with the tools I'm using, in the area I'm using them.