Aussie Bob, were you thinking of the R2800-R3350 etc when you say air cooled aero engine so well thought through, or the flat engines? Obviously they didn't think the induction / injection through on the latter - or did they? Is it true that they never bothered to balance the FA ratios because they had no say on the wide variety of airframes (induction systems) that the motors would be installed on. But then the early Malibu shows what can be done, so why wasn't this done all the time?
I would like to believe the modern flat engine is still a marvel of engineering but I am no engine connoisseur. If BSFC is the measure a TNIO-550 LOP is pretty impressive, but then a diesel is better again...