As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE COMPLYING WITH LYCOMING SB NR 518C, FOUND VALVE RETAINING NUT LOOSE (BOTH ENGINES). RECOMMEND NUT BE WELDED AT FACTORY. NO ATTEMPTS SHOULD BE MADE TO RE-CRIMP NUTS AS THEY WILL FRACTURE AND FRACTURE MAY GO UNNOTICED. SUBMITTER SUGGESTS AD NOTE BE ISSUED.