[Graham Boak]

You can be equally precise in Imperial or metric, and having used both professionally I prefer SI, but once you start converting from one to another you are losing precision not gaining it, plus running the risk of introducing error. For aircraft designed in Imperial it is more precise to use the Imperial. And vice versa, of course.

I have a small number of such books, but I don't think any of them extend to this detail. The RR Heritage Trust would be the best place to ask for help. I have their initial book on the wartime Merlin: I tried looking for it before answering last night but it seems to have gone into hiding.

I have come across a reference to the Hurricane being tested with an RS3M or Merlin VIII. Ho hum.