The factors affecting valve seating wear are not related to valve velocity.No answers to my question about recommended max seating velocity limit values.
They are a function of valve acceleration which will impart a force to the valve greater than
the resisting spring.
This sometimes occurs at the opening ramp but mostly on the flank of the cam.
When the lifter misses the ramp, due to excessive lash, it will impact the flank resulting
in an acceleration spike.
Even if the lifter stays planted on the ramp, it may still see excessive acceleration (force) due to
cam design, excessive rpm, heavy valve train or low valve spring seat force. Or all of the above.
Valve bounce is most often a result of valve float during closing when a lifter loses contact with
the cam lobe, sails over the nose and crashes on the closing ramp. Now the valve might bounce as
much as 1/3 of the total lift.
Carefully measure the ramp height and duration; lash clearance should be such as to locate closing
contact at mid-ramp. If set too tight, the valve may not close properly resulting in overheated valves.
If set too loose, the lifter will crash into the cam flank.
Now where is a Spintron when you really need one?
