Picture of 340/360 head porting....Mistakes?

Well, depending on how far down that is, it could be throat, or bowl, or in between.

On heads where the bowl is bigger than the throat, it’s easy....... whatever the smallest measurement I get is, I call that the throat.

If the bowl is smaller than the throat........ I pick an area near/adjacent to the end of the guide, and call that the bowl diameter.

If the bowl is bigger than the throat, I find the largest diameter I can...... and that’s the “max bowl diameter”.

On a lot of newer cnc stuff, the bowl can be quite a bit bigger than the throat(over .200” difference).