Morris Minor Owners Club

The BMC wksp manual AKD530L states that for the MM that the plug gap (Champion L10) is 0.025".
The BMC wksp manual also states that the spark gap for the Series 2 (Champion N5) is 0.025".

AKD530 14th edition specifies the same plug gaps.

Yes, the discrepancies are interesting, Phil. As before, I can only guess that the suggested smaller gap was something to do with poorer grade petrol back in the early/mid-50's. The S II Operation Manual I referred to came with the car, which is a 1955 model. I'm guessing that the Workshop Manuals you quote are from a slightly later date?
This topic is of historical interest only, I suppose - I have always set my plug gaps at 25 thou and will continue to do so.