What is the point of this?

[Marx3]

I noticed this little fella, sticking out into the barrel on a 18087175, I am about to re-calibrate for a stock 403.
Is this some sort of Venturi vacuum source for the EGR?

[Cliff Ruggles]

Never heard of or seen that carb number, or an extension on that bleed hole on a q-jet......Cliff

[Marx3]

Seriously? :-)
17087175 it says, clearly.
I enhanced the photo a bit.

[Marx3]

It looks to be a regular rear pull-off, single mab unit with ~.078 mabs and 72 jets with pretty thick rods.

I see another guy has a thread right now, about the same carb number.

[Cliff Ruggles]

It's not in line with the idle system fuel supply passage, so not sure what it's function would be? 

If the passage leads to a vacuum supply it would be very weak if it would show any vacuum at all, being that high above the throttle plates.....Cliff

[Marx3]

It looks like it goes to the vacum port on passenger side corner, of the front of the baseplate. I guess this is usually where the EGR get its vacum from.
The position in the barrel looks a lot like that on a Holley with vacum actuated secondaries. That's why I am thinking it is Venturi vacum source. For something, I can't figure out what.

[jamesF]

I noticed this little fella, sticking out into the barrel on a 18087175, I am about to re-calibrate for a stock 403.
Is this some sort of Venturi vacuum source for the EGR?

That 18087175... is what threw Cliff off. 

[Marx3]

Oops. Go figure :-)
170!