"Some versions of the Rolls-Royce Merlin engine used in the British Supermarine Spitfire used the Coffman system as a starter." But not all of them. I wonder

"Some versions of the Rolls-Royce Merlin engine used in the British Supermarine Spitfire used the Coffman system as a starter." But not all of them. I wonder how tight the tolerances were on these engines? When the U.S.A. entered WW2 it was Ford that tackled the problem of making aero engines en-masse. Ford took Rolls Royce designs that had been used for the war thus far (the U.S.A. being a late entrant) and realised that the blueprints provided were not fit for their purposes. Until then Rolls Royce had been making each and every engine in a fairly bespoke way with the parts not exactly interchangeable between engines. Tolerances varied so fettling was always required. Ford fixed this and delivered precision engineering for a much better product. Were the Rolls Royce versions of the engine the ones that needed the Coffman system with the superior Ford versions not requiring it? That is my guess. This was not the end of really-difficult-to-start engines though. Motorsport took it to a whole new level in the post war years. Aero style supercharging didn't last for very long in the pinnacle of motorsport - Formula 1 - due to the thirstiness of the engines. Naturally aspirated engines (with the Ford Cosworth DFV) ruled the roost for many decades and then Renault came along with the turbo. This changed everything. However, to get the turbo to work precision engineering had to solve the problem of extremely high pressure gasses wanting to escape past the piston rings. To fix this the pistons were made 'larger' than the cylinders. So at room temperature, with a cold start, there was no way for mere mortals to hand crank the engine. A very big starter motor in the garage was needed and only at operational temperatures with a little bit of thermal expansion could the engine run freely. The flywheel was very light on these engines so only true drivers could keep these things from stalling, and if stalled whilst on the track, that was that, finito. BMW made the most legendary turbo era engines, 1400 horsepowers in qualifying trim, with the engine having to be rebuilt after a handful of laps. The blocks for these engines came from their 4 cylinder road cars. According to legend the key ingredient for the strength of these engine blocks was urine and cold outdoor weather.