Yep, I was at the Air Force Museum last year after the US Nationals. They had a partial cut-away of a Rolls Royce Merlin. Multiple stage supercharging, four valves per chamber, two plugs per chamber, overhead camshafts, roller rockers. I'm telling you, it looked pretty danged modern.
So, can you imagine an Army Air Corp mechanic coming home after the war, and looking at a flathead V8? No wonder hot rodding took off after the war.