porting and polishing heads

[FallenPhoenix]

Don't forget about the COP ignition system, and different cams and intake. I'm sure that helped add that 45 extra hp

I believe the combustion chamber design was slightly revised too. If anyone has pics of the combustion chambers of a non-pi and pi head, I'd really like to see the difference, if there is one.

 

[bdcardinal]

NPI heads have the emissions shroud by the intake valve. also the chamber volume of the NPI head (51cc) is greater than the PI head (42cc).