The area's in the pic above show you the ares of a stock cylinder head. This is where hand porting is so important vs
cnc machining. Yes a cnc machine can duplicate from port to port without any issues or varience +- . They still need
a skilled cylinder head porter to first go in and do major research and development to have the runner digitized and put into
a cnc program to duplicate the port design.
The areas above are the places i work to get the most out of your cylinder heads that are going to meet your requirements
of your engine size and hp & tq curves. Yes you can just hog out a port , but what you will wind up doing is ruining the
cylinder head. The intake runner needs a rougher finish due to it has a wet flow running through it verse a polished exhaust
port. If you have a mirror finish or hogged out port on an intake runner it is going to do two things.
1) the wet flow of the intake runner will stick and not evaporate quickly enough and will cause rich or lean conditions
in that runner.
2) If the intake side is hogged out you will lose velocity in the runner. Air has to keep the atomized fuel in suspension
from the intake to the valve. If it doesnt the fuel will drop out of suspension and stick to a port floor or wall causing
The exhaust side is expelling gasses that were just burnt in the combustion chamber, so with the mirror/glass finish
it isnt important to have the port finish rouch like the intake side, due to it doesnt have wet flow, its mainly gasses.