"That motor is a thing of beauty. If memory serves me right, they decided to go with a V12 not only for horse power, but isn't a V12 balanced motor in terms of piston throws? If this is correct, I can certainly understand why you would want that for an airplane motor."
The radial engine is pretty well balanced by nature of its design maybe better than a V12. But one feature of the Merlin needs mentioning. It is liquid cooled. When you start sending engines into combat, this is a major consideration.
Without doubt or argument, the Merlin was the most beautiful engine in WW2. It did however have its vulnerabilities. Any puncture of the cooling system meant serious if not fatal engine problems. Radials could withstand more battle damage and chug on. As exciting as it appears to make a few ground attack gun runs in a P-51, some of the glitter starts to rub off when the prospect of losing coolant is considered.
I've always had the deepest respect for the guys who flew WW2 aircraft. Some with the high performance engines would literally kick your ***. Single-engine operation in a P-38 for example ... even though conventional wisdom indicates two engine safety ... offered a high probability a crash on final.
Another neat trick engineers had up their sleeves, engines/props did not turn in the same direction ... depending on which model of an aircraft, like a Spitfire, the transition between models could be a challenge. (Always been amused that Spitfire designers put the landing gear lever on the right side of the cockpit ... have no idea what they were thinking, but I'll bet they never made a formation take-off themselves.)
Nice thread.