I would like to know if a 3 angle valve job is better than a 5 angle valve job and why? I have a 99 Si head and want to improve upon it's breathing so to speak capabilities. I hear that the heads on the Hondas are perfect the way they are and we you use porting and polishing it's a waste of time because Honda makes their engines so well. Any suggestions will help.

 

I don't think DPR and portflow have made a living by making engines worse

There are alot of variables that go into porting a head. It should be custom for every application. You sould find a lot of info if you do a search or check out my sig.

 

Your right, Honda builds some nice engines, especially the heads. They have good ports and 3 angle valve grinds stock. Its probably better that you dont mess with the valves or seats. Some moderate porting and a thourough polish should help a little, You might also consider shaving off about 5-10 thousanths of an inch off the head for better compression. Keep in mind though that any head work on the SOHC d16z motor will get you maybe 10 horsepower at best, and all of that at the high end not throughout the whole RPM band. Good luck