Interesting thread. I have a B20A engine that I was goiing to install in my 1800S (which has a tired B18). I was going to upgrade it to B spec first but I'm also more interested in low end torque below 4000rpm and I notice that the torque figures are not much different between the B20A and B. In fact according to this chart on Wikipedia the DIN torque figure is actually higher for the B20A. Is that really true and if so what advantage in the real world is there for someone like myself in changing the cam and compression ratio (or even retaining the twin carbs, though obviously I will)?
https://en.wikipedia.org/wiki/Volvo_B18_engine#B20