Making the IS 750, 18 cilinders, 3 row in "W", 72 valve, 950 hp, year 1935.
View: https://www.youtube.com/watch?v=292LznS1YIk
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Total displacement was 45,5 liters. it was also used for torpedo boats.
With sleeve valve designs taking so long to develop (Bristol Hercules, Napier Sabre), it would be interesting to explore what if US designs were license built by Bristol, Napier and others.
With the necessary horsepower available, what British aircraft could have been developed and entered...