ON AN OCEANIC FLT ESTABLISHED PROCS ARE EMPLOYED TO HANDLE A NACELLE TEMP OVERHEAT ON A B747-200. WHEN REFUSED DSCNT BY ATC AN EMER IS DECLARED FOR DRIFT-DOWN AND TRACK OFFSET PER ESTABLISHED PROCS.

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FLT WAS DISPATCHED FROM PANC TO RJBB WITH RE-DISPATCH TO RKSI ANTICIPATED BEFORE STAGE. THE FLT WAS NAVING ON 220 DEG RADIAL. DURING CRUISE THE #4 NACELLE TEMP INDICATOR INCREASED TO 5.9. PROCS WERE ACCOMPLISHED IN ACCORDANCE WITH THE FLT HANDBOOK AND THE COMPANY WAS NOTIFIED THROUGH SAN FRANCISCO RADIO HF PHONE-PATCH. AT XA02 UTC INDICATIONS FLUCTUATED TO 6.5 AND ROSE TO 7.0. FLT CONTINUED TO ACCOMPLISH ABNORMAL PROCS PER THE FLT HANDBOOK. THE REQUIREMENT TO REDUCE THE #4 THRUST LEVER LED TO A DEGRADATION OF PERFORMANCE AND THE ACFT COULD NO LONGER MAINTAIN FL370. A REQUEST TO ATC FOR A LOWER FLT LEVEL WAS DENIED. FLT DECLARED AN EMER AND BEGAN A DRIFT-DOWN TO A SUITABLE FLT LEVEL AND AN OFFSET TO THE S OFF COURSE IN ACCORDANCE WITH PUBLISHED CONTINGENCY PROCS. THE FLT STABILIZED AT FL335 AND NAVED PARALLEL TO 220 DEG RADIAL WITH A 25 NM OFFSET. ATC WAS NOTIFIED. THE COMPANY WAS CONTACTED VIA HF PHONE-PATCH; ADVISED OF SIT; AND WAS REQUESTED TO PERFORM A REANALYSIS. PERTINENT INFO SUCH AS LOCATION; FLT LEVEL; TEMP; WINDS; AND FUEL REMAINING WERE PROVIDED TO THE COMPANY. FLT WAS RE-DISPATCHED TO RJTY BY COMPANY. A NEW ATC CLRNC WAS RECEIVED AND THE FLT PROCEEDED TO RJTY VIA 220 DEG RADIAL AT FL330. THE EMER DECLARATION REMAINED IN EFFECT UNTIL ARR AT RJTY.