[scott70]

I've got a 7040267 carb with no ported vac for the distributor. Anybody got a pic of where you'd add that nipple? Signed just curious. Thanks

[Schurkey]

I've added manifold vacuum nipples, but never a ported vacuum nipple.

Ported would be five times as complex as manifold vacuum. Among the issues would be getting the right height of the vacuum passage above the throttle blades. GM (and no doubt others) varied the height based on the application--distributor advance was lower than EGR, for example. EGR took more throttle opening to get vacuum, delaying EGR operation, while distributor vacuum advance happened with very little throttle movement.

Another issue would be whether to use a round hole, or a slot into the airstream--and if a slot, do you want tall and narrow, or short and wide.

Are you drilling the casting(s) at a preexisting boss, or are you completely "winging it" by drilling an unreinforced casting?

Are you drilling "straight in", or does your vacuum passage route through multiple castings with one or more gaskets that also have to be drilled to allow the vacuum passage?

[Tom Vaught]

Good luck with that deal. Best bet is talk to Cliff Ruggles.

Tom V.

[shaker455]

Hi Scott,
In your case adding a ported vacuum circuit into your non-ported carb body and base.
Your all set! carb is done with ported source added.
Come pick it up Sunday along with your curved distributor before you return home.
Hope this helped while the NHRA track event @ NewEngland Dragway got rained out today.
I turned this around the same day for you wile you were down this way...save on shipping
Always happy to help a Pontiac brother!
Thanks