Why just tell them "you have to know where to cut"?
There is no easy answer, there isn't even a complicated answer - it's a book.
Every casting is different, and different again based on valve sizes, chamber shape and volume, lift, RPM, engine size etc.
People looking for an easy answer don't understand the question.
Chrysler used to sell a porting template for the 906/452 RB head, which showed how much material to remove just from the throat at 12 different clock positions, intake and exhaust are different, and left & right handed ports are different. Even if you had it in your hand, if you didn't already know why it wouldn't help you.
Funny thing: when you tell someone the opening & closing figures on a "secret cam", the first thing they do is find one in the Summit catalog with a few numbers that match, and then come back and say "I found it!".
No, you didn't.
Head development is a very labor-intensive process, in which much time & money are spent before you make $1.00 back (and sometimes you never do, except as a lesson: "don't do that again").
Why would someone give that away?
