Street Avenger 570

[pumper]

Can anyone tell me if the 570 I have should be generating vacuum for the distributor advance when only idling?I've had to restrict the vacuum hose with a zip tie to stop it. Is this normal or faulty? I wondered if it was a feature of an automatic transmission carburetor? Perhaps I need to get a different carb or can it be changed? Any advice appreciated. Thanks in advance.

[Danny Cabral]

Carburetors have two distributor vacuum advance ports: Ported (timed) & full manifold vacuum.

Vacuum advance should be connected to full manifold vacuum; not ported.
8°-12° of vacuum advance is the typical limit (some canisters are adjustable).
The (ported) timed spark port is only for emissions/EGR engines (LINK).

[pumper]

Thank you Danny, I would never have thought that based on the carburetor instruction manual. Should I simply block off the Timed Spark source and run a T-fitting from the Full Manifold for the vacuum gauge and the distributor vacuum advance system? My engine tuner seem to think running the PCV from the Power Brake port made it run better, than using the PCV port. Although I don't understand how it's different. Thanks.

[Danny Cabral]

Should I simply block off the Timed Spark source and run a T-fitting from the Full Manifold for the vacuum gauge and the distributor vacuum advance system?

Yes, that's common.

My engine tuner seem to think running the PCV from the Power Brake port made it run better, than using the PCV port.

Find another engine tuner. The power brake vacuum booster should not share the same hose with the PCV valve.

Although I don't understand how it's different.

Both of these components use full manifold vacuum.