As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ADJUSTING VALVE TAPPET CLEARANCE IAW MFG S.I. 1068A, FOUND INNER VALVE SPRING BROKEN ON CYLINDER NR 3 EXHAUST VALVE. NO OPERATIONAL PROBLEMS NOTED. COMPLIED WITH SB388C EXHAUST VALVE WOBBLE CHECK AND REPLACED BOTH BROKEN INNER AND UNBROKEN OUTER VALVE SPRINGS. VISUALLY INSPECTED ALL OTHER SPRINGS. SPRING WAS BROKEN NEAR THE BOTTOM (TOWARDS CYLINDER) WITHIN 1.5 TWIST.