As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) (2) CRACKS FOUND DURING ENGINE ON-CONDITION INSPECTION. CRACKS START FROM BOTTOM SPARK PLUG HOLE AND EACH CRACK GOES TO A VALVE SEAT. THESE CRACKS WERE NOT DETECTED DURING DIFFERENTIAL PRESSURE INSPECTION OR LEAK TEST. INTERNAL BORESCOPE INSP WAS DETECTION METHOD IAW LATEST B041. (TC NR 20070802006)