David Vizard bench flows a BBD 2bbl

I didn't say a wrong prod would shorten lift, I said it might change the overall ratio [ & therefore valve lift ]. Lift could be more. could be less. It will depend entirely on the contact points of the particular lifter.

Why it surprised me that DV failed to mention the above is that in his BBC book he has half a page of rocker arm tests, where some rockers delivered a higher ratio than advertised, others a lower ratio.