1968 GMC C2500 Vapor Canister

[gmc396]

I have a question about the Vapor Canister on my 396 GMC. I've attached a pic below. The large nipple on the canister attaches to the intake manifold. The small one goes to a line that goes through the firewall. I can't easily see where it goes from there. Where does it go and what does it connect to?

I don't understand the function of this canister as there is no line going back to the gas tank; just somewhere behind the dash board. Could I just block this vacuum line at the manifold?

I'd appreciate an explanation.

[geezer#99]

That’s a vacuum can, not a vapor canister.
Likely used to supply a bigger volume of vacuum for possibly the heater controls under the dash.

[gmc396]

Now I see; thank you. The tune-up decal under the hood states to remove the hose to the vapor canister; I don't see one on my truck.

[geezer#99]

Vapour canister(aka charcoal filter) might be located under your battery.

[gmc396]

Nothing under the battery. I wonder if someone put the wrong tune-up instructions under the hood. Looked in Classic Parts and they don't show a tune-up decal for a '68. At any rate, that vacuum hose is old and brittle, so I'll chase those down and replace them. Thanks for your help.

[Steeveedee]

'68 did not have a vapor canister; those started in '70 on light duty trucks- 1/2T (and only California, to boot).

[RustyPile]

Originally Posted by gmc396

Now I see; thank you. The tune-up decal under the hood states to remove the hose to the vapor canister; I don't see one on my truck.

Has the hood been changed on your truck?? Post a clear closeup picture of the decal. The year of application should be printed on the decal..

[FirstOwner69]

Originally Posted by gmc396

Now I see; thank you. The tune-up decal under the hood states to remove the hose to the vapor canister; I don't see one on my truck.

I think you may be referring to the the emissions decal that says step 2 "Set engine timing to specification. (Plug vacuum advance line... this step only)". That refers to the vacuum advance "pot" at the base of the distributor (also in your pic).

The big vacuum can on the A/C housing is related to the A/C system as stated above.

https://www.classicindustries.com/pr...-1199932086060

How are things in Door County?