SO your asking how?
Buy a 14cc head, clone head from a small engine shop ( GX150 5HP clone )
Mail it too me with return postage and I will do it for free.
Then you can see for yourself and copy it for future builds.
if you do a search here you will see a lot of discussion on how to cut the short radius ect but in all honestly its faster and easier for me to port a head then try to explain it all.
There are no impressive gain in power though. A ported head is part of an over all build. It will compliment other modifications.