661kt,
Have a very close look at the POH, paying particular attention to any RPM ranges prohibited by the airframe/engine/prop combination, then use the lowest RPM and highest MP to achieve the performance you want. All these old engines were designed originally for low rpm/high boost, it minimizes the piston speed and maximizes the fuel burn time, and the whole design is crude.
Look at what the engine is certified for, particularly if it has Gamijectors, where you can operate lean of peak ( and also many IO-540’s by original certification), but please don’t ever operate “peak +50 degrees”, you are MAXIMISING the chances of detonation. Deacon is right, but this is not new, it’s just that, in my opinion, TCM and Lycoming are run by the marketing and finance departments, by people who don’t know much about piston engines.
As for how to operate big pistons, Pratt & Whitney and Wright never agreed, Wright always recommended varying the RPM and boost ( for the same SHP) regularly to change the combustion conditions, they always maintained that it would move various deposits more easily , and reduce the probability of plug fouling. But always low RPM, high boost.
I really believe that the temperature control is crucial, the more constant you can keep the temp, the less temp. cycle fatigue. Finally, don’t let the prop drive the engine, the pistons are designed to be pushed down the bore, not pulled, and this goes treble for any geared engine, reduction gears are just that, step down, not step up, reverse loading is death in the afternoon.
Tootle pip!!