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I have a 73 with no charcoal canister and the line capped where the canister used to be. I also have a sealed gas tank cap. I have been driving this for 3 yeas as that’s the way it was when I bought the car and have had no issues. I have seen a lot of talk about this in other forums. Would like to know THIS groups input. Should it have a vented cap since the canister is gone and capped off? Or does it matter? Or what are your thoughts? Just curious. Thanks.
But for what C3 Corvette's. The Cap shown appears to be for later C3 with a thread in cap. If you want a vented cap for a C3 you need a twist style cap. Like this one these.
But for what C3 Corvette's. The Cap shown appears to be for later C3 with a thread in cap. If you want a vented cap for a C3 you need a twist style cap. Like this one these.
The better question is, “Do I need to vent my fuel tank”?
The answer to that question is, “yes you do”.
You need to vent the fuel tank to allow air in and to allow vapors out.
Without a vent of some type you will either implode your fuel tank or the fuel pump may not pull fuel.
The factory vapor canister system did that.
Just because you have the canister disconnected and the hose plugged to it doesn’t mean your system is actually sealed.
The fuel separator on the side of your 73’s fuel tank could be non functioning or cracked and venting there.
The rubber hose from the separator could be disconnected, missing or cracked and venting the tank there.
The line running between the tank and the canister could be cracked and venting your tank.
The fuel cap itself could have a bad seal or the prior owner may have modified it to vent the fuel tank.
My bet is, your tank is venting somewhere.
If you go for a long drive and remove your cap, are you getting a large amount of pressure when you crack the cap?
If not something in the system is venting the tank.
If you do get a lot or even a little pressure, something is wrong, it will, at some point cause you possible serious issues or simple ones, and just replacing the cap may not correct the problem.
If your tank and all lines in the system are sealed up tight, you do need to vent the tank with a vented cap.
Last edited by OldCarBum; Jul 10, 2022 at 03:15 PM.
The better question is, “Do I need to vent my fuel tank”?
The answer to that question is, “yes you do”.
You need to vent the fuel tank to allow air in and to allow vapors out.
Without a vent of some type you will either implode your fuel tank or the fuel pump may not pull fuel.
The factory vapor canister system did that.
Just because you have the canister disconnected and the hose plugged to it doesn’t mean your system is actually sealed.
The fuel separator on the side of your 73’s fuel tank could be non functioning or cracked and venting there.
The rubber hose from the separator could be disconnected, missing or cracked and venting the tank there.
The line running between the tank and the canister could be cracked and venting your tank.
The fuel cap itself could have a bad seal or the prior owner may have modified it to vent the fuel tank.
My bet is, your tank is venting somewhere.
If you go for a long drive and remove your cap, are you getting a large amount of pressure when you crack the cap?
If not something in the system is venting the tank.
If you do get a lot or even a little pressure, something is wrong, it will, at some point cause you possible serious issues or simple ones, and just replacing the cap may not correct the problem.
If your tank and all lines in the system are sealed up tight, you do need to vent the tank with a vented cap.
thanks for your info. I’m assuming it may be vented somewhere but don’t know where. I haven’t had any issues so I’m just going to keep driving it. I don’t smell any gas fumes in my garage. So I don’t know.
Over the past 50 years, I’ve owned numerous, boats, jet skis, motorcycles, and cars with vented fuel caps.
I’ve never smelled gas fumes in any garage.
But I also never store anything in the garage with a full fuel tank.
i know the purpose. Just don’t know if mine is or not. I’ve been driving it for 3 years the way it is. No canister. Plugged line. Sealed cap. No issue.
again I will ask. Why do I need a vented cap when I’ve been driving 3 years with a sealed one and no canister.
The photo I posted was from a 1973 Corvette. Your original system had the Emissions system plus on the tank backup vent as in my photo. So adding an additional vent would be backup vent a originally intended.
The photo I posted was from a 1973 Corvette. Your original system had the Emissions system plus on the tank backup vent as in my photo. So adding an additional vent would be backup vent a originally intended.
No just a suggestion that if there is an issue with vent on your tank. Then if it is clogged no air will enter the tank for the missing fuel as you drive. Air has to replace fuel used.
What Everyone keeps telling you is that you need to make sure your tank is venting somehow properly.
Either with a vented cap or some other method.
If you are happy thinking you are good, then do nothing, or you could find out how your tank is venting and either fix it of just leave it.
Your car your choice.
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Gas cap
