Weber Venturi size question

[SRT356/911]

I have a set of Weber 40 Ida's

The OD of the venturi's measure 46mm and are marked and measure 36mm ID at the top. They widen to 40mm at the bottom- ID.

The butterflies are marked as 78 and the bottom of the throttle bodies measure 40mm.

PMO sells venturis marked with a range of 40/xx and 46/xx.

What should the bore of a 40 Weber throttle body be? Same for the 46 throttle body? When I measure 46mm in the throttle body is that correct for a Weber 40?

Are the butterflies opened to 46mm on Weber 46's?

[1QuickS]

All Weber venturis for the three barrel carbs used on our engines are 46mm OD and the diameter in the top of all the throttle bodies is 46mm. The ones for 40mm throttle body bores have a 40mm exit diameter and those for the 46mm throttle bores have a 46mm exit diameter which is essentially a knife edge. This is why the grub screws retaining the 46mm venturis have a cylindrical nipple as opposed to the drill point nipple used for the 40mm throttle bodies, the 40mm throttle bodies have a 3mm wide step to stop the venturi from moving toward the throttle shaft and the positive engagement of the cylindrical nipple is all that retains the venturis for the 46mm bores.

The "78" denotes the ellipse angle of the throttle plate; 46mm throttle plates are 46mm wide and made with a 12 degree inclination from horizontal.

[SRT356/911]

Great, thanks