Shortround6
Major General
P-40 started in deliveries in May.
310 P-40/Tomahawks (ex french) were completed by the end of Sept. First Deliveries of the ex French aircraft started Sept 18. Sept production was 114 planes.
The US got 200 P-40s before production was stopped to handle the French/British orders. The US army would get the rest of the planes later but improved models
However, the Early Allisons needed to be reworked and were remanufactured (n 1941). They were de-rated in US service (but not British) to 950hp at 8000ft.
This involved two main problems.
One was that the US Army wanted to rate the engine at 1090hp at 13,200ft(?) instead of 1040hp at 14,200ft.
Two, this change affected the engine life and the engine would no longer meet hours of operation goal the army wanted.
The engines were remanufactured, but the British didn't get any.
The Allison engine had passed two type sets, on at each power rating but the 1090hp rating took a while and it failed the first attempt/s.
However the Merin was rated at a 100 hour test and some foreign engines couldn't make 100 hours it may not be that important.
In any case the P-40s being delivered in the summer and early fall of 1940 to the US (and to Britain) did NOT have armor, BP glass or SS tanks.
The ones that attacked Pearl Harbor were ALL manufactured after April 1941. There were a lot of small differences in the wings to solve a structural issue.