Hi,
without details as to why the valve broke, all I can say is; it is not normal for a valve to "just break". Usually it's because the valve has come into contact with the piston due to timing belt snapping, or if you turn an engine over after having the head off, but haven't set the timing belt correctly. The latter would be a schoolboy error and highly unlikely if the mechanic was any good. Material failure of valves is very rare (i.e. just snapping and dropping into the pot)
Cheers
Ken Chapman, April 2007
