motor problems

Did the timing belt snap per chance?

The engine is not an interference engine. It is physically impossible for a valve to touch the pistons (unless you were to get huge lift cam and/or mill the head a whole bunch for compression). Even then, the valve will compress the spring instead of causing damage to the valve or piston. I doubt this is your problem.

I suppose it is possible a valve broke off...

can you turn over the engine after taking out the spark plugs? You could also stick a screwdriver in the spark plug hole and feel for an obstruciton in the cylinder.

Then, I'd probably pull the valve cover and look for problems. Then, pull the head.