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.

[Snapafun]

Different question, although putting it here to keep it on this particular type of carb. Today I installed my new Avenger 570 and nervously did a couple of things to ensure a "from scratch" installation. Basically I removed a QFT Slayer VS 750 from our FE390 1964 vintage, and included in the removal the soft x2 stackable spacers fitted between the inlet manifold & carburetor. The inlet seat for the carb appears to be much better in condition than the aged spacers, so torquing the carb onto a fresh gasket felt heaps better. To allow this mounting, I needed to bend the lower section of the primary accelerator. (I think this would normally be used in some specialty application) to allow free throttle movement.

Then there's the PCV connection. I had to route the hose from the PCV valve along the Starboard side of the carb and up to it PCV connection. It would appear the the previous installation had the PCV connected to the Power Brake coupling on the QFT carb for convenience, and I think done because our 1964 Mercury Monterey doesn't have a brake booster. So I guess I'm asking for comments to better understand for giving alternative options should that be preferred. Your opinions most welcomed.

[Danny Cabral]

I had to route the hose from the PCV valve along the Starboard side of the carb and up to it PCV connection. It would appear the the previous installation had the PCV connected to the Power Brake coupling on the QFT carb for convenience, and I think done because our 1964 Mercury Monterey doesn't have a brake booster.

It doesn't matter that your vehicle doesn't have a power brake vacuum booster. The PCV valve just needs to be connected to the full manifold vacuum port on the carburetor. You can connect the PCV valve to the power brake port, since it's not used.

[Snapafun]

So I guess that means that Jan gets to wonder at why so I say, "Planning ahead babe - Disc Brakes maybe?" She holds the budget, so one step at a time. Thanks for your feedback.

[Danny Cabral]

You're welcome.