As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT HEARD TICKING NOISE AT FULL POWER FOR TAKEOFF. TAKEOFF ABORTED. SUBSEQUENT GROUND RUNS DETECTED DEFECTIVE INTERNAL BAFFLING IN FORWARD MUFFLER ON LT ENGINE. APROXIMATELY 50% OF INTERNAL BAFFLING WAS MISSING AND REMAINING PORTION WAS FLOATING FREE. A NEW MUFFLER WAS INSTALLED.