valves broke off stuck in piston, they were lodged in the metal of the piston, what causes this
2 Answers
an "interference engine" is one where the valves will contact the pistons if the timing is off. Usually a broken or jumped timing belt/chain is the main cause for that. You may have also lost a rocker arm.
Broken valve spring, broken valve keeper, broken timing belt or chain, engine overspeed are a few of the causes.