76 Vette vacuum cannister plumbing

I have an Assembly Manual (AIM?) for my Corvette but the page on this item doesn't depict anything but a vacuum hose from the cannister to the original Qjet.

My 383 has an Edlebrock AVS 650 carb on it and I've been running it with the cannister purge hose going to a manifold vacuum port on the carb. The ported vacuum port handles the vacuum advance, and the only other one availble is the large one for the PCV.

Running the cannister to the manifold vac source on the carb however, appears to cause a slight vacuum leak. When I pinch the line going to the cannister on a hot engine, it changes the idle.

Is there supposed to be a check valve in there? Or is it designed to go to a ported vacuum source?

These '70s Corvettes have a tendency to smell like gas when they are hot and parked in the garage. If you go to the Corvette Forum's site & visit the C3 Corvette Tech section you'll see how common it is.

With this cannister unplugged the car smells worse than ever so I want to connect it again. But I don't want to run it to the manifold vac source on the carb, if it's going to act like a vacuum leak. Therein lies the rub - is there supposed to be a check valve in the line of some type?

I wish the Thunder AVS Carburetor had another ported vacuum source. I don't want to tee into this, as I want to make sure there's always enough vacuum for the distributor advance to work properly. Guess I could try running manifold vac to the distributor & the ported vacuum to the cannister.

Thanks for any suggestions.


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I have the same problem with my truck when I switched from a Quadrajet to an Elelbrock Performer, and folks told me to T into the PCV hose and use that source to purge the vacuum canister.

I had it set up that way (with the T) for a while and the engine seem to run fine. However, I disconnected it and took out the T later on because of hose routing problems (I needed to have a longer hose to ensure the PCV valve would not pop out of the valve cover) and haven't plugged it in again.

Bruce