please tell me what this means


thanks
-Mike

 

The'inertia' of the weight of the valve at high RPM[missed shft say] allows it to 'hang open' [hopefully NOT touching piston, though it's possible..]
Weak springs, overrevving, etc. is the cause..

 

When it doesn't close with the time of the cam's actuation. Basically the cam causes the valve to open and close, if the springs are worn out or if the motor gets over revved then instead of the lifter following the cam lobe it will experience a condition where it will jump [or bounce] over a section of the lobe causing the valve to remain open beyond the time when it should be closing or closed.

 

The cam opens the valve due to the action of the lifter on the lobe. It is up to the springs on the valve stem to keep the lifter in contact with the lobe by exerting a force on the spring's washer, hence, "closing" the valve when the cam rotates allowing the lifter to ride down the back side of the lobe. When the RPM's exceed the spring's ability to keep this contact between the cam and lifter, we experience valve float. You may also see the valve bounce off its seat which reduces combustion chamber pressures and results in a loss of power.