Power outputs

[Bob Culver]

I raised this question when I first discovered this Forum years ago and suggested that all the engines to the 3 bearing must have about the same max bhp based on performance as per contemporary road tests and present day owners (although all could have been non standard). Such heresy from a rank outsider, and colonialist to boot, caused a furore (rivalled only by my later observations about lapping)! 
RN updraught seem to at least match the RP and often better the more streamlined early Ruby! There was a cr increase in 1933 but the top end performance may have been reduced by more constricted breathing.  (Alan supplied bhp figures for about 1935) The Williams Specials book lumps them all together at 13 bhp but the publication is riddled with errors.
At the time the makers may have considered it more prudent to quote hp at then normal operating revs and not as driven by men young in the 50s and 60s.
I have a bhp curve for a late marine engine but this may not exactly match the car version..