Vacuum advance issue

Cam1399 said

I have a mild 360 in a 1974 duster with vacuum advance issues. Trying to see if I’m doing something wrong or if it’s the vacuum advance. Idle timing is at 11 and wide open is 34 with the vacuum advance plugged. I have edelbrock carb. The one I’m hooking it to is the passenger side. As soon as I hit the throttle the timing goes crazy and starts pinging. Thanks guys

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Are you connecting the vaccuum hose to a manifold or ported vaccuum port on the carb? Does the RPM go up when you connect the hose? If you are using the ported vaccuum port, there is no vaccuum present at idle, but as soon as the throttle is opened you get vaccuum.
With manifold vaccuum, the idle will pick up as you put the hose on. Adjust idle speed with the vaccuum advance connected. If you check timing with the vaccuum connected it may be 30° at idle. Light load and cylinder density is low. This is OK. Do not change from vaccuum disconnected timing. As you open the throttle the vaccuum advance will back off and centrifugal will come into play.
If you have connected to the ported vaccuum, you are getting vaccuum advance added to centrifugal and a dense mixture in the cylinder with the throttle opened. Way too much advance. A vaccuum gauge on the port you are using will also clear up whether you are on the ported or manifold port.