Vavle angle
A valve needs to match the angle ground into the head in order for it to seal when fully closed. This one angle isn't meant to help performance just seal the chamber, resulting in abrupt corners and not allowing for optimum flow. Now if you take the valve and grind another lesser angle on the inner seat portion and a greater angle on the outer portion it allows the air an easier path to follow, less abrupt and results in better flow. That is a three angle valve job and five is two inners and two outers. You could have a 100 angle valve job if you really wanted, but the more angles cut into the valve results in less sealing area which could be a problem as well.
Air doesn't flow very well through a tube, or port in this case, when it has to exit an outlet with sharp 90 degree edges. It causes vena contracta.
A valvejob gives the air a more gradual turn to exit the port, improving flow characteristics and gives the valve a better surface to seal. Every angle effects the flow through the port, even the seat angle. Just because it has more angles, like a 3 angle vs. a 5 angle, doesn't mean it is any better either.
A valvejob gives the air a more gradual turn to exit the port, improving flow characteristics and gives the valve a better surface to seal. Every angle effects the flow through the port, even the seat angle. Just because it has more angles, like a 3 angle vs. a 5 angle, doesn't mean it is any better either.
