Thanks GF for posting that RR Merlin video. An equally amazing feat was how Packard undertook the production of Merlins under license from RR here in the US. They ramped up the production very quickly with the assistance of other companies.
I helped a friend one day after he had to scrub a flight in his P-51 due to the tachometer not working. Since he did not have a key to his own supply room we had to check the tach generator to see if it was the problem and fix it. We pulled the cowlings and I proceeded to remove the generator off the right rear head. As I was unbolting it I happened to look at the valve cover and noticed the word Maytag cast on it. I told my friend I didn't know that I was riding in something powered by Maytag. He laughed and asked me if I knew what Maytag's main work was before the war. I thought about it and replied they were an aluminum foundry and he said yes and said they made the valve covers along with other parts.
Many of us know about companies producing totally unrelated products during the war that was different from their normal work. Things like Remington producing rifles and car companies building fighters, bombers, radial engines and Goodyear building Corsairs. The question is could we ever pull such a feat off again as so much material and production is outsourced from overseas?