There's no correlation between the engine type letter and the cam. B18A does use the "A" cam, but B18B and B18D had the "C" cam (the later ones, at least). B20B used the "C", B20 E and F the "D"

Phil,
That's what I thought. But since my new Dutch buddy said that if I asked him for a cam for a MP/Volvo tractor with a B18 engine, he would sell me the same cam that came in the Amazon, and since the Amazon with the B18 was sold in Holland (and here) only with the A and the C cam, except for some specialized vehicles maybe, I assumed he was talking about the A. I made that assumption on the basis of our having discarded the C as a potential candidate for single carb application.

In your reply to Mike you seem to rule out the A cam because its peak hp and torque comes at much higher rpms than the Norwegian article says is the case for the B18C engine in the ST257 tractor. Is it your opinion that the "kamvinkel" (cam angle?, overlap? - as Weberman suggests) is not consistent with a C cam as well? Or is it possible that they are using a C in combination with a single carburetor especially set up for use with that cam? The article Erling has so graciously translated for us goes into a fair amount of detail about regulators, which I assume to be governors. Do you think that might factor in, aside from holding the revs steady under varying loads?
Bob S.