I remember clearly the incredible figure of a 4.75 min. climb to 20 000 ft. for a in-service P-47M pulled from service for the test. This was from a complete article on the P-47M. Full fuel, full ammo...
To put it in perspective, the Me-109K supposedly does 4.5 min. (I heard the oil-circulation problem at nose-up angles, while using MW-50, was solved by the K model: Any clues on that? I know it wasn't solved on the G-14AS in November 1944 yet).
The best climbing in-service prop fighter of WWII? AFAIK, The Spitfire Mk IX with 150 octane pulling 80" MAP: 4.2 min. to 20 000 ft.
Worthy of note is that European theater P-38Ls used 150 fuel at 64" MAP, but the British mix of lead was poor and tended to foul spark plugs or cause other maintenance problems. There were no such problems with US-mixed 145 Av gas in the Pacific... P-47s and, to a lesser extent, the P-51s, accepted the British 150 fuel better.
I heard of engine cutting-out problems on take off for the P-51 though, killing several pilots... Erosion of the valve seats was determined as the cause, and a new mix of the 150 fuel alleviated the problem only in very late 1944, if not 1945... These cutting-out issues were initially dealt with from July '44 by much more frequent maintenance and occasionally "reving-up" the engines in flight to clean them... I even think there was a call for a return to lower octane 130 fuel for the continent-based aircrafts, were maintenance was harder, but 150 fuel remained for UK-based fighters... This is all from memory, but should give a rough idea of the issues...
Gaston
