What was found
A LOUD KNOCKING SOUND EMANATED FROM THE ENGINE COMPARTMENT. SHORTLY AFTER, ENGINE BEGAN TO EXPERIENCE SEVERE VIBRATION AND LOSS OF POWER. THE RAM DROPPED TO 1,100 DEGREES, OIL AND FUEL PRESSURE REMAINED NORMAL. BUT AIRCRAFT CONTINUED TO LOSE POWER AND ALITITUDE. THE INSPECTION OF THE ENGINE REVEALED NR 3 EXHAUST STACK MOUNTING FLANGE AND SEVERAL STUDS WERE BROKEN. EACH CYLINDER HAD NORMAL COMPRESSION AND THE ENGINE OIL SHOWED OBVIOUS SIGNS OF METALIC PARTICLES.