Cool heads don't give to much HP without ported cylinders. I did pretty much every bolt imaginable before I got my motor ported by HJR and never noticed any big changes. Once Kevin did a dune port it was a completely different machine. If I were you, I would spend the $300-400 and get a nice port job done by Kevin at HerrJugsRacing. You will notice a substantial gain in power, especially if you use 19cc domes and go to race or Avgas. Give him a call anytime, he is very friendly to talk to and will give you the advice your looking for.
Www.herrjugsracing.com
(760) 703-1836