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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,224
The vacuum solenoid has nothing to do with boost retard.
Nobodies gonna loose any sleep if you wanna think so though.

The vacuum solenoid is kind of like a single pole double throw switch. It has 3 vacuum hose connections so it can be hooked up and used two opposite ways when voltage is applied while the 3rd remaining connection is vented to air.

In the origonal configuration it blocks air from flowing through the 2 vacuum hoses connected to it when voltage is applied so there is no vac retard on cold starts and the timing advances and the idle raises.

After a couple minutes the voltage is taken away and the spring loaded internal solenoid valve relaxes and opens and lets intake manifold vacuum through to the inner distributor pot and retard the timing at idle and during deceleration, in the origonal configuration.

Now the one in my car has a much more useful purpose.
I use it with the hoses hooked up differently so it blocks air when no voltage is applied and passes air between the 2 hoses connected to it when voltage is applied and I'm using it as a "boost clamp" on the WUR with an adjustable rpm switch.
The remaining hose connection is vented to air with a downward curved hose to keep rain water from getting in.
Old 04-06-2010, 02:57 PM
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