This thread is supposed to be about the new, but now postponed, electric bike plans but what the hell, I’ll accept the old Cosworth Challenge.
Roy Bacon’s book “Norton Twins” has a good section with pictures on the Challenge and quotes 65 bhp at the gb output for the road bike and 95 bhp for the racer.
Derek Magrath’s book “Norton The Complete Story “ also mentions the Bob Graves/ Quantel effort and shows the steeply angled intakes and quoting 120 bhp.