over reving can cause damage to all engine parts .what is the causes and how it happen and why?

Answer 1

The major cause of damage to an engine from revving the engine above it's maximum RPM limits is primarily due to a condition called "valve float". As the engine speed increases above maximum, the valve springs can no longer retract the valve fast enough and the intake and exhaust valves actually begin to float between their open and closed positions, never achieving either position before being moved again. Eventually a valve will contact the piston and it's game over...

Racing engines use valve train components ( valves and springs) that are very heavy and capable of pulling the valves shut at the higher RPMs they turn. Production car engines use much lighter weight components...

In addition to valve float, high RPMs can cause connecting rod caps/bolts or wrist pins in the piston to fail, hence the term "throwing a rod". Everything in an engine has mechanical limits to which they are designed.

Answer 2

the cause is your right foot is too heavy

how it happen? high engine load give stress, heats.. then al breaks aparts

and why..?? build a race engines