A PA30 R ENG HAD TWO CYLINDERS AND VALVES DAMAGED INFLT. AN ENG ANALYZER USED TO CONFIRM THE POWER LOSS CAUSE. THE FLT DIVERTED TO A NEARBY ARPT.

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ON ROUTINE PATROL; MADE TURN TOWARD ZZZ1 PROCEEDED ABOUT 1 MI AND EXPERIENCED PWR LOSS THAT EMULATED WATER IN FUEL. SWITCHED TANKS TO MAINS (FROM TIPS) AND DEPLOYED ELECTRIC FUEL PUMPS; MIXTURES MOVED TO FULL RICH. BRIEF PERIOD 1-2 SECONDS OF APPARENT IMPROVEMENT; THEN PWR LOSS RETURNED ACCOMPANIED BY VIBRATION AND YAW TO R (MINOR). SCAN OF GAUGES REVEALED REDUCED FUEL FLOW R ENG (12+ GPH ON L; 9+ GPH ON R SIDE). REVIEW OF ENG ANALYZER REVEALED 0 EGT AND CYLINDER HEAD TEMP ON #1 CYLINDER R ENG. DAMAGE LIMITED TO ISSUES WITH EITHER 1 OR 2 CYLINDERS ON R ENG; 1 VALVE AND ITS CYLINDER DESTROYED; POSSIBLE DAMAGE TO #2 CYLINDER (BASED ON PERCEIVED INCREASE OF EXHAUST GAS TEMP NOTICED AFTER PWR LOSS). NO INJURIES OR AIRFRAME DAMAGE. R ENG DEVELOPING PWR SO LEFT ONLINE. MADE IMMEDIATE TURN TOWARD NEAREST SUITABLE ARPT AND NOTIFIED ATC OF SITUATION (OUR COMPANY SAME AT TIME). AIR CREW MAINTAINED COMS WITH ATC AND REQUESTED DEPLOYMENT OF READY HELI; WHILE ACFT COMMANDER ATTEMPTED COM WITH COMPANY THEN WITH APCH. ATC ADVISED PROBABLE UNAVAILABILITY OF READY HELI AND WE MAINTAINED COURSE OF ZZZ2. ACFT AND SYS STABLE AT THIS TIME. EMER DECLARED WITH APCH. PROCEEDED TO ZZZ2 AND LANDED WITHOUT INCIDENT. THIS OCCURRED QUITE SUDDENLY AND IT IS POSSIBLE I HAD UNNOTICED WARNING FROM THE ENG MONITOR A FEW MINS PRIOR TO THE INCIDENT BUT DID NOT NOTICE DUE TO CONCENTRATION ON NAV AT THAT TIME (REQUIRED TURN). SUCH NOTICE WOULD NOT HAVE MADE MUCH DIFFERENCE SINCE WE WERE WELL OFFSHORE. ALSO; MANY TIMES HIGH CYLINDER HEAD TEMP AND EXHAUST GAS TEMP READINGS ARE PROBE ISSUES AND CONFIRMATION BY OTHER MEANS IS NECESSARY. THERE WERE NO OTHER SUCH WARNINGS; AND THE MECH NOW WORKING ON THE ACFT SUGGESTED THERE WAS PROBABLY NOT MUCH WARNING HERE. ACCORDINGLY; THIS INCIDENT APPEARS TO BE ONE THAT IS ALWAYS POSSIBLE WITH PISTON ENGS AND MUST BE MANAGED. NO CORRECTIVE ACTION INDICATED ACCORDING TO THIS WRITER; EXCEPT TO CONTINUE THE POLICY OF USING ONLY MULTI-ENG ACFT FOR MISSIONS SIMILAR TO THE INSTANT CASE. CERTAINLY; SINCE DIAGNOSIS WAS MADE EASIER BY USE OF THE GRAPHIC ENG MONITOR; INSTALLATION OF SUCH DEVICES IN AS MANY ACFT AS POSSIBLE IS RECOMMENDED; ESPECIALLY IF OPERATING IN ENVIRONMENTS THAT CAN BE DANGEROUS; SUCH AS THE OFFSHORE LOCATION OF THIS INCIDENT. ALL ACFT OCCUPANTS WERE WEARING PFD'S AND A SUITABLE RAFT WAS ON BOARD; AS WELL AS 2 EPIRBS; ONE WITH GPS; ONE WITHOUT. ACFT COMMANDER PUT ONE INTO FLT SUIT; THE AIR CREW TOOK THE OTHER.