Valve Contact Points
Valve contact is the term I have always used to describe the point on the opening side of the cam profile where the valve first starts to move. On the closing side, this point is where the valve first makes contact with the seat. These points are on all cam profiles, both solid and hydraulic. I do not think this is an official cam design term, as I have heard other terms used.
The valve contact point is used when designing the cam profile ramps. On a solid cam profile, the valve lash will be determined by where the valve contact points are and the rocker arm ratio used. Some cam profiles are designed without much attention given to the ramps and the valve contact points. The valve contact and the lash is decided on after the cam profile is designed. I do not do this. I design the ramps first, based on the type of cam profile and the application. I then design the cam profile and mate it to the opening and closing ramps. On both a solid and a hydraulic cam profile, the valve contact points will determine the velocity at which the valve will open off and close on its seat. The proper location of the valve contact points will contribute to a smooth and reliable valve train for the application.
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