Vapor canister on vintage cars


A few decades ago I replaced the V6 in my psuedo-street-machine with a more muscular V8. At the same time, all the smog equipment went with old the engine.

Here we are in 2021 and I’m wondering about installing a new fuel vapor canister and vacuum control valve. Given that the car only sees occasional weekend cruises, I’m wondering if its worth the money and effort.

Design / engineering questions:

  • with the driving / parked ratio being so low, will the charcoal saturate while the car is parked?
  • how long of a drive is required between periods of being parked to fully refresh the charcoal before it sits again?

Any educated perspectives would be greatly appreciated.


I’ll give you some additional design considerations;

  • Was there a V8 option for your car?
  • Was the evap system different for the V6 and V8?
  • Are the factory parts even available for this mystery car? (you don’t tell us ANYthing about the make model or year)
  • Do you have the technical ability to design an evap system for your car?

As for your design considerations, neither are a problem with a properly designed evap system. We’ve just gone through a year of many, many, cars being driven as you describe yours will be and none of them have had evap problems. Battery problems, sure, but not evap problems!

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Thanks for your reply Mustangman. To answer your questions:

  • yes, the 350 small block was an option on the 1980 Camaro
  • although the emissions systems were very similar on the V6 & V8 builds of that year, the only parts that are still with the car are the PCV components
  • no, I’m not planning on designing an evap system for my car

My thought, if I was going to, was to replicate something from the early '70s where PCV and the charcoal canister were the only emissions controls installed at the factory, as discussed here.

I asked the question the way I did because it’s a very generic topic of interest to anyone with a car of similar vintage. In regards to the pandemic parking lots we’ve observed - did anyone do any testing to prove the evaporator systems continued to perform day after week after month after month of parking without the charcoal becoming saturated - and that it just keeps on absorbing? My guess is probably not …

It’s only a guess on my part, but I’d expect the charcoal to saturate faster in the summer than in the winter.

The cars themselves did. A saturated canister will cause the dreaded short-click on the fuel filler at the gas pump (been there, done that!). Breaches or failure of the system will cause a check engine light on any modern car (post '96). Neither of those occurred. We did not get any more complaints than usual here about that.

If you want to re-introduce such a system to your '80 Camaro, I’d duplicate the the V8 system from that car that year… assuming you could get parts for a 41 year old car. Seems little different from a 1975 Camaro, the first I see these parts listed on RockAuto.

Why do you want to do this?

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Interesting, the newer emissions systems sure are a lot more complicated than the ones from the '70s! To get a better handle on what you were talking about I had a read of this.

Having worked on industrial emissions monitoring systems, when the charcoal in the NOx analyzer vacuum pump circuit was exhausted, we’d see the rubber NOx pump diaphragms start to deteriorate due to exposure to O3 - the canister didn’t plug. Saturation-wise, I was expecting something similar with the fuel vapors - but rather than passing ozone, I expected they’d stop absorbing the fuel vapors and pass them to atmosphere anyway.

Having driven the car with an open to atmosphere tank vent was the result of a lack of time and interest, but it always bothered me. Now, that I have the time and the interest, I just wanted to make sure it would do what it was supposed to do given the car’s operational characteristics.

Then just return it to 1980 specs for a V8 if you can obtain the parts. Use the factory diagrams. You might have to substitute parts for those that are not available anymore.

You have some research ahead of you to accomplish this.



Thanks for the feedback, but as indicated earlier, I’m only interested the early '70s version - adding the vapor canister and control to the existing PVC.

This car did not have a vapor canister in the early 70s. Not until 1975. I don’t know any that did as I don’t believe that was a requirement in the early 70s.

As I said, if that is what you want, you have some research to do.

If I felt compelled to control fuel tank vapor I would connect a hose between the tank vent port and a fitting on the air filter housing.

But that wouldn’t handle the long periods when the car is parked.

The diagram at the bottom of this chat is looking like what I was contemplating. Just need to identify the canister with valve or canister and valve to be purchased. Too bad some of the vintage parts suppliers use stock photos that do not accurately depict the actual parts.

The prolonged parking periods are still a concern, but at least the vapor canister will capture what it can absorb which is probably better than the tank being open to atmosphere.

So why ask here? Why not ask on the forum you linked.

Failing to get an answer on the other forum, order the part you think you need and send it back if it isn’t what you expected. Note the chart is for a truck which lagged behind cars in emission controls. Look for the canister in truck parts.

My un-educated guess is no.
I appreciate your concern, which I understand to be fuel vapors escaping to the atmosphere. Your vehicle’s contribution is negligible compared to all the other sources, I.e., lawn equipment, boats, earlier collectible vehicles, and farm equipment.

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I guess I am missing something here . If the fuel cap is on and good just how much vapor is there? There are classic cars all over the world that are parked for long periods of time . Yes gas should not go in the air at all but is this really a big problem . I think it would do more good for people to switch to battery powered home lawn equipment.

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As my gas powered equipment goes, it is replaced with battery powered.

The vapor canister is missing from my 1973 Duster, after shutting off the engine on a hot day there is a strong gasoline odor from the front of the car. Gasoline vapors escape from the hot carburetor and fuel tank uncontrolled.

I should have bought a replacement vapor canister years ago but I didn’t give it much thought. The next time I visit the pick-a-part I am going to look for something suitable from an old Mopar.

Remind people of that the next time someone overreacts to a missing catalytic converter on a fuel injected vehicle, there are a lot more hydrocarbons escaping from a breached fuel system than the tailpipe.

Just to say, someone stole the 3 gallon tank from our little boat. Bought a new one. it sits in the open bow 12 foot boat. Gas tank was designed not to let pressure out. The heat of the day expanded the gas to such a pressure it spewed raw gas out the little 7 horse and into the air and water. First day I probably did more than you will do in a lifetime, but I appreciate your concern, Can you get a setup at the scrapyard from a slightly newer model that will work.

Nevada_545 - came across this Mopar write-up in my travels. Although it’s from 4 years ago, it includes references to some still-available part numbers that may be of interest for you.

Thank you, that is an interesting article about the early evap systems. I have a 1970 Dodge with the ESC system that stores the fuel tank vapor in the engine crankcase.

The part numbers shown come up as discontinued or not available. ACDelco 215153 is of a similar design and inexpensive. I might try that one and eliminate the risk of an old canister filling my carburetor with charcoal granulates.