I WATCHED BOTH OF THE CLIPS. I HAD A SIMILIAR PROBLEM (unidentifiable rattling) it sounded a little louder in the clip so I'm not sure if its the same,BUT AFTER I TIGHTENED EVERYTHING DOWN, OPENED THE VALVE COVER AND INSPECTED, GOT A VALVE ADJUSTMENT,TOOK OFF THE OIL PAN AND FOUND A SMALL C-CLIP AS BIG AS A DIME, PULLED THE MOTOR AND YANKED APART THE BOTTOM END THINKING IT WAS SOMETHING ELSE TO FIND IT WASN'T, WHEN THIS WAS ALL OVER I LOOKED AT THE HEAD CLOSELY LIFTED THE ROCKER ARMS TO FIND A LOST MOTION ASSY HAD CAME APART. THE CLIP THAT I FOUND IN THE OIL PAN HELD IT TOGETHER SO IT WAS NOW MAKING FULL TRAVEL UNTIL IT HIT THE BOTTOM END OF ROCKER PIVOT. SO I ASSUME THAT IT WAS CAUSING THE ARM TO SLAP AROUND UNCONTROLLED. IT IS STILL APART AT THIS TIME BUT I'LL FOLLOW UP ON THIS. HOPE THIS HELPS IT TOOK ME SEVERAL MONTHS TO FIND THE PROBLEM.