BMW: 325e timing belt, interference engines, exhaust stroke

Question
Tonight on the way home from work, my timing belt broke on my 1986 325e while I was driving. The belt was only about 4 years old (12K miles). I'm guessing my engine is screwed now, but was wondering if there was a chance that it's not. Any body ever have a belt break while in motion and not have other damage?

Answer
Bill,
 This is most unfortunate, I'm sorry to hear that this happened to you.
 
 Yes, I have heard of this happening, and it usually ends badly.  The timing belt keeps the valves in time with the pistons that are moving up and down.  BMW's are "interference" engines, and this means that if a valve is all the way down, and the piston is all the way up... they will make contact!
 There are engines that dont do this, but they are rare.

 Usually what happens is the belt breaks, the valves stop in the position they were in, and the pistons keep moving and usually impact the valves, and bend them.  The minimum that will need to be done is to pull the cylinder head off and check all the valves and piston tops.  

 Hopefully all that will need replacing is a few valves (not all of them would make contact, just the valves that were on the intake/exhaust stroke.

 good luck
 Josh