As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT WAS FLYING WHEN THE ENGINE STARTED SHAKING AND CYLINDER 1 CHT AND EGT WENT COLD. PILOT DECLARED AN EMERGENCY AND LANDED AT KRDG. UPON REMOVAL OF THE COWLING THE INSPECTOR NOTED THERE WAS A HOLE PUNCTURED IN THE CYLINDER #1 ROCKER COVER. IT APPEARS ONE OF THE INTAKE ROCKER ARM ATTACH BOLTS HAD SHEARED CAUSING IT TO PUNCTURE THE ROCKER COVER. UPON REMOVAL OF THE ROCKER COVER AND REMOVAL OF THE ROCKER ARM THE OTHER BOLT CAME OUT WITH THE HELICOIL.