Definition of quantal. 1  1 [Latin quanti how many, plural of quantus] : of, relating to, or having only two experimental alternatives (such as dead or alive, all or none) 2  2 [quantum] : of or relating to a quantum.
3. Engine movement. Another symptom of bad or failing engine mounts is an engine that moves in the engine bay. If the engine mounts are in good condition, they should be able to secure the engine firmly in the engine bay.
When the engine exhaust valve becomes stuck open, it can not only lead to the valve burning, but may also cause the valve to become broken if it gets hit by the piston. Valve breakage and burning are the two most common causes of valve failure.