As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENGINE, MECHANIC WAS CHANGING LEAKY PUSHROD TUBE SEALS AND REMOVED LIFTERS TO BLEED OUT OIL. NOTED FACE OF LIFTER TO BE SEVERELY SPALLED. ASSOCIATED CAM LOBE WAS WORN AND STEPPED. REMOVAL OF REMAINING LIFTERS REVEALED VARIED DEGREES OF SPALLING ON ALL INTAKE LIFTERS. NO DAMAGE WAS NOTED ON EXHAUST LIFTERS. ALL INTAKE CAM LOBES SHOWED SIGNS OF WEAR. THERE WERE NO SYMTOMS OF THIS PROBLEM.