I had very little dealings with the Foden stroker but I know many folk who ran them and, if driven correctly, they were fine. You needed to keep them above the 2000 rpm range otherwise they tended to overheat, my last gaffer drove one when he worked for Bernard Swain and Tommy Babb who has the restored S21 cabbed mixer on the show circuit both said the same. The 12 speed box was developed to make this easy. Tommy’s has the extra cooling tank mounted on the dashboard in the cab to keep a good head of water above the engine which the later versions were fitted with, a lot of the problems were caused by drivers used to Gardner engines etc driving the two strokes the same but you had to forget all that and really ‘drive’ them like most 'strokers including the Rootes TS3 which took some getting used to. When I toured the Foden works around 1976 they were still building them for The Admiralty as they were fitted in pairs into their high speed launches.
Pete.