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72 Spider Charcoal Canister plumbing

Posted: Thu Nov 04, 2021 7:03 pm
by 72Spider
Hi all,

I’ve gone through all previous posts regarding the subject above but have not located a definitive answer to my dilemma so I thought I’d post the question.

Bone stock 72 Spider, charcoal canister is missing. Have sourced said item and now need to connect it.

I understand the connections from the gas tank venting apparatus as well as the line to be connected to the intake manifold.

As for the third input line my Haynes manual, on page 62 describes it as ‘connecting to the air cleaner’.

On page 64, however, it shows a diagram identifying this connection as the ‘fresh warm air pipe’

and shows a graphic of a connection for this hose emanating near the exhaust manifold.

I am unable to locate pictures showing this connection but the manual states it ‘draws warm air from the air cleaner’.

Does anyone on this list have a stock 72 with this setup and if so could you please provide a picture?

Obviously my car lacks this item, fresh warm air pipe, and it will most likely need to be fabricated, which is no big deal, just looking for someone familiar with this specific setup for a bit of advice.

Great forum, lots of good info here!

Re: 72 Spider Charcoal Canister plumbing

Posted: Fri Nov 05, 2021 10:51 am
by 18Fiatsandcounting
I'm curious about this myself, for my '71 spider. I have done some researching in the manuals and looking at old photographs, and while I have seen a reference to this warm air pipe, I have never seen one. Not even a photo in an old car.

The way this filter works is that gas vapors from the tank go into the bottom connection of the canister, and the top connection goes to a metered orifice into the intake manifold. The warm air pipe then warms up the activated charcoal and the vacuum from the intake connection sucks the accumulated vapors into the intake where they are burned.

That's how it's supposed to work, but as mentioned, I can't figure out this warm air connection. So, here's what I did on my '71: Bottom connection on canister goes to metal line back to the gas tank. Top connection on canister goes to intake manifold. Side (or another top) connection goes to the vent connection on the float bowl cover of the carburetor. My theory is that the canister is near the exhaust manifold so it is warmed already, so maybe that warm air connection isn't really necessary? I think all you really need is a source of input air to the canister so the intake vacuum connection doesn't keep pulling vapors out of the gas tank when the car is running.

I don't smell any gas, and it all seems to work fine. Anyone else have a better explanation/idea?

-Bryan