Not sure if this is relevant or not. The Convair 440 had BMEP gauges which gave a remarkably accurate indication of power. The starboard engine had a compressor which furnished the air conditioning and extracted power from the engine to do so. On take off with equal manifold pressure (54"Hg I think) the left engine BMEP gauge would indicate 235 BMEP and the right engine indicated 225 BMEP reflecting the power loss. During the take off run and as the CHT increased for the same MP both BMEP needles would show a gradual decrease in power reflecting I presume the hotter charge. The BMEP readings by coincidence seemed to indicate a rough approximation of the horse power. Example being 235 BMEP is around 2350 HP.
If after an extensive run up the CHT was quite higher than usual and a take off commenced, there was a definate reduction in the BMEP readings.
This makes an interesting point concerning light training piston aircraft where one frequently sees students conducting high power "burning out" of fouled spark plugs which have given a big mag drop. Prolonged high power increases internal engine heat and in a twin engine aircraft if by misfortune an engine fails after lift off, the already "hot" other engine already degraded in power will maybe not permit a positive rate of climb. Morale being that prolonged high power on the ground might clear the plugs but exposes the aircraft to lower climb rates. All this theory from observing BMEP gauges! Maybe I am right or wrong in this speculation but it seems a logical assumption?