How much lower valveguide is really necessary?
 

I'm working on home-porting some gt-40p's and gone through mouse's home porting tutorial (and everythingh else I can get my hands on) in addition to logging hours of practice with my dremel on some old 351C heads so I get the feel of polishing metal. Seems like some of the biggest gains to be had are football shaping the valve guides (amongst other things). I was thinking........

How much valve guide really needs to be hanging into the ports? What would happen if I smoothed the entire valveguide down and blended it in so only the valvestem itself protruded into the port? I mean... There _does_ seem to be enough guidesleeve in the "upper" part of the guide to keep the valve straight without any problem.

Is there some harmonic/vibration issue at hand that I need to take into account? Granted I have never seen a ported head without valveguides at all......

What do you all think? Am I being crazy again? What if I just shortened them?