Probable Cause:
1. Broken Valve Spring(s) Or Locks
Install new parts where necessary. Broken locks can cause the valve to slide into the cylinder. This will cause much damage.
2. Loose Bolts Holding Rocker Arm Assembly
Tighten to 24 ± 7 N·m (18 ± 5 lb ft).
3. Too Much Valve Lash