As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SPINNER BULKHEAD INSTALLED FOR STC SA7633SW LIQUID COOLED ENGINE INSTALLATION WITH PROPELLER MODEL 3AF365C514-C/G-80VMFA-2 FOUND CRACKED NUMEROUS TIMES ON OTHER AIRCRAFT WITH SAME MODIFICATION. APPEARS THE MACHINING OF METAL FOR BULKHEAD MATERIAL IS ROUGH CAUSING STRESS AROUND HOLES.