As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE ENGINE COMPRESSION TEST, CYLINDER NR 1 SHOWED 10/80. A VISUAL INSPECTION CONFIRMED A CRACK EMANATING FROM THE LOWER SPARK PLUG HOLE TO THE COOLING FINS, APPROXIMATELY 1.50 INCHES LONG. THIS IS A RECURRING ITEM, OPERATOR KNOWS OF AT LEAST 12 OCCURRENCES OVER THE LAST 2 YEARS.