1955 Where to tap vacuum for idle mixture adjustments?

[Surf Green]

Only had my '55 since December and still learning the machine. Been trying to get the carb properly set and in order to get the idle mixture screws adjusted right I want to attach a vacuum gauge. Where should I attach this? I have a brake booster which has a vacuum line--should I tee off of this? What is the general recommendation? Pictures would be extremely helpful to this newb, also.

Thanks!

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[CSPIDY]

The power brake booster should work for your needs
it takes vacuum from the manifold, should be ideal

 

[Frankie the Fink]

That should work, it just has to be FULL manifold vacuum and not ported vacuum...
I don't know if these early cars have a vacuum advance but that's normally where I
install a "T" when tuning (on Chevys)..

 

[zeroroadkill]

Off the top of the fuel pump (wiper vacuum)?

 

[jimntempe]

Off the top of the fuel pump (wiper vacuum)?

No, that would be the wrong place as it's not manifold vacuum, it is an artificial vacuum that will exist even when actual manifold vacuum is gone. That's the whole reason for that vacuum pump, to create a vacuum when the "normal" vacuum isn't available.

 

[zeroroadkill]

No, what I mean is disconnect the input side of the fuel pump vacuum line that runs directly to the manifold and put your vacuum gauge there. That is a direct line to manifold vacuum. At least on my engine, the input side of the fuel pump has a line that goes directly to a brass fitting at the base of the carburetor into the manifold.

 

[jimntempe]

No, what I mean is disconnect the input side of the fuel pump vacuum line that runs directly to the manifold and put your vacuum gauge there. That is a direct line to manifold vacuum. At least on my engine, the input side of the fuel pump has a line that goes directly to a brass fitting at the base of the carburetor into the manifold.

Oh yeah, my bad. I was thinking you meant the other side of the pump. Yes, you are spot on, that would be a great place to hook it up.

 

[Surf Green]

Thanks for all the input, fellas. Looks like on my engine the brake boost vacuum line and the fuel pump vacuum line both originate from the same manifold port (see photo). So I suppose it doesn't make a difference as to which one I use. I'll give this a whirl in the coming week and hopefully get this carburetor dialed in correctly.