ok, i think im gonna port my heads im putting on my new motor. they're 76cc's 1.94 valves. heres the questions i got:
1. when gasket matching the intake ports, how much can i actually grind out of the hole? i mean, i know if i go too far ill be into the pushrod hole, but how much do i need to leave so it wont crack or anything? i got a old head out of the woods to practice on, i just dont know how far i can go without worrying about cracking.
2. im trying to avoid taking much metal out of the combustion chamber, the damn things are huge already, so i dont want to lower my compression any more, so whats the easiest way to polish them wihtout taking out much metal?
3. what other areas should i focus on? im new to this, and i REALLY dont wanna **** up my heads.

i got a dremel and a few grinding bits for it, what else do i need?

thanks in advance