Ive been told that detonation can cause the cracks around the ears

Stress and strain causes metals to fatigue and eventually crack.  Combustion pressure, thermal expansion, and vibration produce stress.  Increasing power usually increases combustion pressure.  Detonation can create some extremely high pressure spikes superimposed on top of what ever combustion pressure is present.  The pressure spikes from detonation in a stock engine can be a lot higher than the peak combustion pressure in an engine with state of the art power levels.