My 1998 Ford Escort starts, 5 seconds later dies and has a clattering noise. A mechanic said the timing belt was broke but other people say it wouldn't start if that were the case???????

Can a car start and run even for a few seconds if the timing belt is broke.  One
mechanic told me my timing belt broke causing so much damage that I needed a new
engine. Another Mechanic told me that a seat vale failed and sinked into the head and
that I need the head replaced.  I have no idea what to do.  Several people have told me
that if it were the timing belt that the car WOULD NOT start, period, even if it is just for
a few seconds.  Help.