Again thanks for the education guys. 
shane.
valve centerline angle
Moderator: Team
valve centerline angle
Darin, Meaux, CBoggs. When designing a cylinder head how do you determine the proper SSR height and port height to valve centerline? Darin mentioned that not having the proper SSR Height, the engine will "shut off like a light switch" at upper RPM. What causes this? Meaux talked about increased velocity over the short turn apex on 23 degree heads,but in a port that is raised wouldnt this be less of a concern? I'm not trying to start anything, I really dont understand it. Again thanks for the education guys.
shane.
Again thanks for the education guys. shane.
I can't answer your question directly, but I'll bring some ideas up for comment..
If you look at Darin's picture http://webpages.charter.net/dsda/CUTAWAY-011.JPG you'll see my reference for the following.
If the port floor (and roof respectively) were moved up vertically in the area of the hold-down bolt, the turn toward the valve would become sharper in that area. If it were lowered vertically, the turn would become less, however it would then be greater right near the seat (down lower).
It could then be said that for any given "package" there is an overall compromise that will yield the best results. I'm guessing it's some kind of a general rule of thumb range of relations. Once something along those lines is established, the port could be tested and tuned as needed. It might also just be an experience thing.
Most of the junk I work on has a much tighter SSR than that, so I'm usually stuck with what I have to work with. I.E. haven't dealt with the opposite extreme.
SWB
If you look at Darin's picture http://webpages.charter.net/dsda/CUTAWAY-011.JPG you'll see my reference for the following.
If the port floor (and roof respectively) were moved up vertically in the area of the hold-down bolt, the turn toward the valve would become sharper in that area. If it were lowered vertically, the turn would become less, however it would then be greater right near the seat (down lower).
It could then be said that for any given "package" there is an overall compromise that will yield the best results. I'm guessing it's some kind of a general rule of thumb range of relations. Once something along those lines is established, the port could be tested and tuned as needed. It might also just be an experience thing.
Most of the junk I work on has a much tighter SSR than that, so I'm usually stuck with what I have to work with. I.E. haven't dealt with the opposite extreme.
SWB