I took my 96 gsr to a mechanic, they took off the head and told me that the one of the pistons seem to be hitting the bottom of the head. He also turns the head over and metal fragments (non aluminum) fell out of the head. He then tells me it maybe cheaper to get a whole new engine instead of total rebuild. The cheapest engine he could find was 2200. Should this engine be scrapped or salvaged? What can cause the piston to go too far up?

 

"What can cause the piston to go up so far"

Over revving.