Vacuum advance source
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From: Niceville, FL.
Depends on the vehicle/engine. My '83 F350 with the 460 uses manifold vacuum, straight when cold and through a restrictor when warm. Many others us a special port on the carburetor. The correct vacuum routing for your vehicle should show on its vacuum diagram.
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From: Niceville, FL.
There should be a port (ported vacuum) on the carburetor that has little or no vacuum at idle but produces good vacuum as the throttle is opened a little. That would likely work best. But, manifold vacuum would work too, little higher idle speed probably.
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From: sunny san diego
Originally Posted by Piffery1
Depends on the vehicle/engine. My '83 F350 with the 460 uses manifold vacuum, straight when cold and through a restrictor when warm. Many others us a special port on the carburetor. The correct vacuum routing for your vehicle should show on its vacuum diagram.
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From: Niceville, FL.
I could be wrong, the restriction is in the line going to the top port on the thermally operated valve which I thought was open to the center (vac adv) port when the engine is warm.
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I tested my vacuum advance today and i sucked on the vacuum hosed as hard as i could and no movement inside the distributor cap do i need a new vacuum advance switch?
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Joined: Jun 2004
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From: Niceville, FL.
Waltg78, If it was the hose going directly to the advance unit then I'd say yes. Especially if you could continually suck air. But first try to move the advance mechanism by hand just to see if it's binding or broken.