that last post is certainly interesting. I think conventional wisdom today is that it was sort of the other way around: FR Porter departed Mercer over disagreements on engine design. He wanted the next engine to be overhead cam, which he perceived was the future (patterned on Peugeot). The board/management , presumably for economic reasons, disagreed, and chose to go with Eric Dellings L-head designs which were successful race engines and far cheaper to manufacture than OHC. Porter went on to start his own company, FRP, which failed, but not before producing prototypes which had OHC engines.
Edit: in fact just reading up a few posts, Seal Cove museum has one of the very few (only?) FRPs on display.