Many moons ago I was inspecting the compressor of a Bristol Proteus on a Britannia using the intrascope to see if the bump stalls it had experienced over the Gulf of Mexico had damaged any blades. They did and the first stage had some rather twisted ones. No rips or tears or missing bits but still a bit questionable. The local Bristol representative showed up and gave us some guidance. Basically, if no rips or missing bit and none of the blades were twisted into a reverse pitch direction, it was okay.
It turned out he had been assigned to Trans Canada during their use of the Bristol Freighters with the Hercules engines. According to him, in the winter's cold, if you didn't have preheaters going, you would have to wait for spring to start them. I had experienced the problems of starting poppet valved engines, particularly carbureted ones in the cold but I can imagine trying to get sleeves to reciprocate and oscillate inside the cylinder in the cold wilds of Canada. Don't know if he exaggerated or to what degree. Any comments on cold weather ops with those engines?