C3Hawk

Dub (or anyone) can I pick your brain for a second. I decided to start a new thread since the vapor canister on my Vette is way simpler than Zorro's '79.

I have a 1975 small block with all the pollution stuff long since removed. The car is running really well, I'm just trying to reduce the gas smell in the garage. There is a smell of fumes coming from the canister.

In this picture, the top shows the canister top with the "tank" vapor inlet and the "carb" outlet which they previously cut. The bottom pic shows the bottom of the canister with the vent open to air.


Questions:
1. If I just connect the gas tank vapor line to the "tank" inlet and connect vacuum tubing from the "carb" outlet to the ported vacuum of my Holley carb am I done?
2. What's the best method to check patency of the fuel tank vapor line?

Thanks!

cardo0

Ok, one last post for the night.

For #1:

U have one fitting that connects from the fuel tank which is actually the tank vent - that runs the drivers side and connects through a backflow/check valve to the top of the fuel tank.

Another fitting that connects to the ported vacuum on the carburetor to digest the fuel vapors above idle speed to prevent stalling the engine. Yes u want a carb port that is above the throttle blades when closed - locate with fine wire or WD-40 spray/carb cleaner spray.

The bottom fitting can be left open and is for the purge air as the port vacuum opens on the carb it draws air in that bottom fitting.

I thought it had a third fitting for the fuel bowls but i guess not after looking for one. Other cars do though.

Something else i found is that the charcoal filter should be removed and replaced every 24 months according to the GM shop manual though no sells the filter itself - canister only. And the newer canisters have all the fittings on the top of the canister (including the purge fitting/port).

For #2:

Compressed air will do if u have a compressor or even a can of compressed air/computer air cleaner/circuit board air cleaner should do it. It would easier if u had a helper at the other end to listen/feel air flow. I would disconnect the fuel slosh check vlv at the tank to protected it from harm. That check vlv is a little float ball device and i guess low air press wouldnt hurt but who know if that old plastic will crack?

C3Hawk

Thanks those connections fits with what I thought, too. I might take the lazy route and get one of the new canisters you mentioned if I don't feel like messing with the sealed original unit.

I do have to figure out how to get to the connections by the gas tank to check the line.

Thanks again!

You might be interested to see these filters I found at Summit:

(To the admins, please just delete pic if it violates the forum policy. No harm intended.)

Zorro O

If you run the ported vacuum line through a TVS (thermo vacuum switch) on it's way to the canister. It will keep the purge from happening until the car is warm. That is basically what the electronics on the newer cars do. This will keep your car from getting to much gas when it is cold.

Zorro.

DUB

card0 pretty much hit the mark on this one.

No temperature vacuum switch (TVS) is needed.

If you get a charcoal canister that as another port on the top with a small fitting in it at the valve on the canister. That small port goes to to your carburetor vacuum source...and the marge line goes in with your PCV...where you get a PCV withe the 'T' fitting at the top of it.

Do not be surprised if your vapor line is plugged or split open. I have changed out more than I can remember.

DUB

C3Hawk

Thanks all!

cardo0

I do have to figure out how to get to the connections by the gas tank to check the line.

I was able to access the vlv and tubing once i removed the drivers rear tire. I could reach in and change everything there. Kinda working in the blind for the most part though as i couldnt see much with my arm in there. I recommend looking it over or even make a drawing before pulling parts out.