Upgraded on the later V4s GB - along with much else. Sadly, never really a very successful beast - even when subsequently blessed with water cooling and all manner of other improvements. (Mind you, there was some serious competition in those just-pre-war years when supercharging was the new big thing. Somewhere just north of 50bhp I think - not sure how that stacked up against the BMWs and Gileras.)
The Porcupine was the next cunning plan - but then the bansturbators stepped in to outlaw all forms of forced induction . . . .
Sammy Miller has a phenomenal V4 in the museum, or did when I was there last.
