pistons/sparkplugs

My boyfriend has a BMW 318ti standard. We took the car to a mechanic who specializes in import cars.. he told us that the pistons were hitting the spark plugs...then we talked to a different mechanic who we don't know if we should trust and he told us that it was impossible for the piston to hit the sparkplug....and that the car had to go way over the rpms and that after that the piston broke the head... which mechanic should we believe? and we want to know if its possible for the piston to hit the spark plug and cause the car to basically die?  

There was an similar issue with Mustang GT. Yes it is possible. But it depends on the type of piston you are using. There are some spark plug make which are around 3mm longer then the standard once and can hit the piston. Take an experts advice first.