I know, But the rush of air though the small holes could upset the running ?.
Nope Greg, Australian, that's actually Ken Phelp's Norvin!Hmmm......... updraft manifolds........very British.
For what it's worth, on the flow bench adding a bellmouth to a 1038 Concentric increased the flow by 0.8%, but on a 1036 it decreased it by 0.3%. However, the differences are small enough that I'd have to say the bellmouth made essentially no difference within experimental error.What is about the original small bellmouthes on the Amal 276 and 289 carbs?Any influence on power delivery?
I did on my desktop dynoYes... but did you test it on your dyno?