United Racing Engine Failure

The exhaust valve was placed back in the seat for this photo. The face of the valve actually snapped off at the stem.

Here you can see where the face of the valve broke off. The head of the valve bounced around and destroyed the cylinder head.

This is the lifter. The roller broke clean off. Guess where the needle bearings went.

These are AFR 227 cc Race Ready Heads. AFR states that the heads have 60/40 valve spacing and require shaft mount rocker arms. The rocker arms removed from the engine are of the stud mount type. If my photo was better you would be able to see fret marks and ware on the under side of the rocker arm where they did not clear the valve springs. So maybe the malfeasance of installing the wrong rockers is the smoking gun in this United Racing Engines catastrophe. Could it be that the rocker prevented full valve retraction causing the piston / valve contact that eventually broke the valve.