Ported vs manifold vacuum

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Sep 13, 2011 | 09:37 AM

bigvette1

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From: Schaumburg IL

Ported vs manifold vacuum

On a 73 or for that matter any C3 with the vacuum cannister, does the vacuum line from the cannister get manifold or ported vacuum from the carb? Is there a difference in the cannisters operation by vacuum source? Thx

Sep 13, 2011 | 10:17 AM

C6DuffMan

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From: Roseville CA

Pretty sure it's manifold.

Sep 13, 2011 | 10:54 AM

MelWff

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Definitely manifold since you need it regardless of throttle position.

Sep 13, 2011 | 11:02 AM

joewill

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From: Indy Indiana

you want be able to immediately be able to raise your headlights after your car starts. only way to do that is with the manifold vacumm.

Sep 13, 2011 | 11:35 AM

Mike Ward

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It's pretty much irrelevant since '73s had TCS.

Sep 13, 2011 | 12:24 PM

MelWff

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Sounds like this thread has run into confusion as to whether we are talking about the distributor vacuum advance unit or the vacuum cannister to run headlight doors, wiper door etc.

Sep 13, 2011 | 01:46 PM

bigvette1

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From: Schaumburg IL

Let me clear that issue up. Has nothing to do with distributor or headlights. What I was referring to was the vacuum line that goes from the carb to the charcol cannister. Along with this is the PCV line from the carb to the valve cover to the charcol cannister.

I was wondering if you hook into ported or manifold vaccum (or referred to as above or below the carb butterflys. Thanks.

Sep 13, 2011 | 04:33 PM

7T1vette

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From: Crossville TN

There are 3 hoses going to that charcoal canister (on my '71, anyway). One comes from the fuel separator gizmo mounted to the left side of the fuel tank and transfers tank vapors to to canister for temporary storage; one goes from the canister to the front of the carb base (on my car, this line goes to the PCV valve where it Tee's together and then goes to that carb base connection). The third hose is the 'signal' hose from the carb to the canister. It trips a valve in the canister which allows the captured vapors to be sucked up by the intake manifold. I believe that this hose IS from a ported fitting on the carb, so that the canister operates only when the throttle plates are cracked (not at an idle condition).