As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE WAS INSTALLED ON THE AIRCRAFT AND RUN UP. AN OIL LEAK WAS NOTICED IN THE LOWER SPARK PLUG BOSS AREA OF NR 1 CYLINDER. FURTHER EXAMINATION REVEALED THAT SOME CUTS BETWEEN FINS ADJACENT TO THE SPARK PLUG HOLE NEARLY PENETRATED THE THREAD AREA OF THE SPARK PLUG HOLE. CYLINDER NR 2 HAD A SIMILAR PROBLEM BUT THE CUTS ONLY PENETRATED HALFWAY THROUGH THE BOSS SURFACE.