Originally posted by livelyjay
"port out"
The term porting is a leftover from old American Iron heads, where you would typically "hog out" the ports as much as possible, literally boring out the ports to the largest available size. This produced more power simply because the engines didn't flow very well in the first place, and there was practically nothing you could do to make flow any worse.
On import heads, it is more of a portmatching and polishing process.
P&P cliffs notes:
They match the ports to the gasket size, but do not remove excess material. Next they remove any casting flaws or flash, and polish the surface relatively smooth (not a mirror polish, some roughness is good.)
Next they just clean up all the angles inside the port, do a valve job (3 angle, 5 angle, radius, whatever), and polish out the combustion chambers.