How to Replace the Vacuum Advance Unit of a Chevy

by Dan Ferrell

The procedure to replace the vacuum advance unit varies little from one Chevy model to another. However, engage the new advance unit correctly during installation for proper operation. Once you have the correct replacement for your Chevy model, taka a few steps to remove and install the component.

Remove the Vacuum Advance Unit

Step 1

Detach the vacuum hose from the vacuum advance unit attached to the distributor. Click on the link provided on the Resources box, at the bottom of this article, for an image of a typical vacuum advance unit, if necessary.

Step 2

Remove the distributor cap by unscrewing the two mounting screws using a Phillips screwdriver. On some Chevy models, you only need to rotate the screws about 1/2 turn to release the cap.

Step 3

Pull the rotor off the distributor shaft. On some Chevy models, remove two mounting screws using a Phillips screwdriver.

Step 4

Unscrew the two advance unit mounting screws using a standard screwdriver.

Step 5

Pull the advance unit slightly outward, and then rotate it to disengage the unit operating rod from the metal strip.

Step 6

Remove the vacuum advance unit from the distributor.

Install the New Vacuum Advance Unit

Step 1

Set the new vacuum advance unit in place.

Step 2

Rotate the unit slightly and engage the unit operating rod into the metal strip on the distributor.

Step 3

Screw the two advance unit mounting screws using the standard screwdriver.

Step 4

Install the rotor on the distributor shaft. Tighten the two mounting bolts, if your rotor model is equipped with them, using the Phillips screwdriver.