Failed Rocker Arm

Seen this type of random failure on a single rocker, replaced one on a stressed Opel race engine and kept going. No need to believe the others are going the same route IMHO. So replace that 1 or replace them all as you think fit.

Having said that, I would:

• Roll the pushrod across a very flat surface to be sure it is not bent
  
• Examine the lifter under that rocker to be sure that the retaining clip is still in the top of the lifter. If not, then it pumped out, the valve hit the piston, and then the first thing to give was the rocker.
  
• If the clip is missing replace lifter
• Push down on the valve at the stem to make sure it moves freely.
  
• Then, put in another rocker, and turn the engine over slowly to make sure that nothing is binding.
• Then run compression test on all cylinders; you want to make sure that valve is not bent
  
• If all OK, then start engine and check