bad noise with a 22r

my cousin has an early 90's 4runner with a 22r. he just had the clutch replaced. 2 days later when starting up it sputtered so he reved it which resulted in a boom a clunking noise and a rough idle. a mechanic said it is a bad valve and he needs a new motor (he did not take the motor apart yet). is there a chance the pistons are ok and he can get away with just a head replacement? need help asap, thanks!

 

Well, if it still runs then the timing chain did not break. I suppose it could have jumped a tooth and caused the piston to hit a valve. I have not had this happen to me, but have seen a few heads where the pistons hit the valves due to timing belts breaking. Never seen any major damage to pistons from this, I would say he has a good chance of just putting a head and timing chain on it.