Valve float is an adverse condition which can occur at high engine speeds[1] when the poppet valves in an internal combustion engine valvetrain do not properly follow the closure phase of the cam lobe profile.
There is also a significant risk of severe engine damage that can include valve spring failure, pistons contacting the valves, or catastrophic lifter and cam lobe failure, especially with roller lifters.
Properly optimizing the valve duration avoids undue stresses to the camshaft lobes and tappets.
By reducing valvetrain mass, valves can close more rapidly with a given spring stiffness.
Since the 1960s, Italian motorcycle manufacturer Ducati has used a desmodromic valvetrain to counter this problem and allow for higher engine speeds by using positive closing as well as opening of the valves, without springs.