Rocker Failure

[g356gear]

I went to take the car for a spin today and enjoy the weather a little. I warmed her up and then proceeded down the road. About 1/4 mile into the trip I noticed the sound of an exhaust leak or puffing from the driver side exhaust. A few seconds later I start to hear a light tapping from the motor. Instantly I pull it over, shut it off, and pop the hood. Everything looks OK. Start it up and I get a loud tapping from driver side #1 cylinder. Pull the spark lead and it stops. Great....something let loose in the new motor. Managed to limp it home and pull the valve cover and this is what I found....





None of the parts of the rocker actually broke off....just spread like an orange opening up. I spotted a few very fine particles but nothing major. So now I would like to find a good quality upgrade rocker set that I can still fit under my stock 396 valve covers. Any ideas?