The Sol-Vac & Idle Speed Adjustment

The Sol-Vac is an idle speed adjuster that is a two-part vacuum and electric solenoid. The plunger opens the throttle a little to increase idle speed under certain conditions. The vacuum-operated portion increases the idle to 1100 rpm. The electric solenoid part raises the idle to 900 rpm. The computer determines which one and when.

DETAILS

If the engine is running okay otherwise, there is a simple test for proper Sol-Vac operation. Warm the engine fully. Shut it off. Restart the engine. It should idle at 1100 rpm for 15 seconds, then drop to 900 rpm for 45 seconds, and finally drop to curb idle speed of 680 rpm (These numbers are for the manual transmission).

To test the vacuum portion of the Sol-Vac, run a vacuum hose from the nipple to a source of manifold vacuum. The plunger should pop out and raise the idle to 1100 rpm.

To test the electric solenoid portion of the Sol-Vac, unplug the wire coming from it. Connect the wire coming out of the Sol-Vac to a jumper wire going to the positive battery post. The solenoid isn't powerful enough to push the throttle open, so manually open the throttle a bit and the solenoid should engage. Release the throttle and the solenoid should hold it open just a little, raising the idle to 900 rpm. Remove the jumper wire and the solenoid should disengage, dropping the idle back to normal. (Be careful with the jumper wire: accidentally touching it to a ground, such as any part of the engine or car body, could result in damage or even an engine fire.)

Idle-Setting Procedure

Setting the idle with the Carter BBD is a four-stage process. The engine must be thoroughly warmed up to operating temperature and all electrical accessories must be turned off.

Remove the jumper wire. Reconnect the Sol-Vac vacuum hose. Reconnect the Sol-Vac holding solenoid wire.

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