Thanks, good to know that they can be made to work. The big question remaining is how does a guy make the "intermediate circuit very soft"?

Thanks for the post Mike. Making a comparison to the 525 sc. Here's a page out of B&Ms technical info. Looking at the chart merc should have chosen a 950 cfm carb for a 454 ci engine runnning 5 psi. Despite that they chose to have a dominator flange casted into their blowers and went with a 1050 dominator.

Seems like to me that carbs for blower motors are ofter chosen to avoid any restriction in the inlet of the roots blower. Guys often run two 850s with a 6-71 or ever two 1050s with a 8-71.... I've read that they often pick up boost by using larger cabs and eliminating the restriction.

Using the chart for my motor ~460 ci and 7.5 psi, we actually land on a 1050 cfm carb.... Like merc with the 525 sc, I'll be about 100 cfm over the recommendation... This is how I came up with an 1150....
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Edit: Forgot to mention; at high elevation guys often over carb and jet down. Not sure that it always works out but I'm gonna try it...

Mike I was surprised as well but thought I'd throw it out there. Evidently prosystems thought otherwise. Not sure but I still have the build sheets for 454/177 builds.

remove the air bleed from the circuit.the oriface is big&pulling air instead of fuel.

When I changed from 850 boost referenced to Nickerson built 1050's on B and M 174's in my 311 Formula I picked up 400 RPM. Had to buy a set of props.

that's what I'm hoping for!

Thanks! Is this doable on the old 3 circit carbs too? Or just the newer models with the changable bleeds?

Also, would you remove the air bleed restrictor all together or start putting larger bleeds in until it leans out?

i would remove the bleed and see how it responds,then go from there.

Would you bother with running a PV on a 3 circuit? If so just the primary? or both?

that depends on the application,p v in primary circuit but not to common in secondary side.