For example on an h22. I completely built the engine besides the head. No, I don't plan on leaving it this way but for now, it will have to do. I'm just wondering how much the stock head on an h22 can take.

At what point do the valvetrain what not reach it's limit?

 

...or does it matter? becuase I talk to some people that say the h22 head should be able to handle ~700hp but you just won't get as much hp gain as if you had a built head. So is that true? Can I actually leave my head alone while I run my turbo (over 20psi) and not have to worry about damaging anything on the head?