Gas Cap - Vent or No Vent ?

[huladick]

I need to replace my gas cap on my 1980 C3 with a locking cap. Do I need the vented or non-vented type ? Thanks

 

[Dave L.]

The original GM part# for your gas cap is 22503147. My shop manual states "To protect the tank from mechanical damage in the event of excessive internal or external pressures resulting from the operation of this closed system,a pressure vacum relief valve,located in the gas cap,will control the tank internal pressure".

Dave

 

[Jeffro]

I'm pretty sure it needs to be vented. The only unvented caps I have ever heard of from the factory were on 70 LT1's and they were quickly replaced due to problems.

J

 

[Tom73]

I thought that starting in late 69 all Vettes used un-vented gas caps as the vent was then built into the gas tank itself. Most 69's and earlier used vented gas caps as the tank did not have its own vent.

But you would be safe with a vented cap, would just have two vents then (cap and tank).

tom...

 

[huladick]

Thanks for the input. I'll with vented.

 

[DDLS3]

Your original equipment cap is unvented. The vent line runs through a charcoal canister in the engine compartment to reduce VOC emmisions. You may smell gas fumes in the cabin if you drive with the windows down using a vented cap. I replaced my cap with a non-vented which eliminated the fumes and gas smell.

 

[huladick]

Uh Oh..... Now I'm getting confused.

 

[78SilvAnniv]

I had that problem!

Vented gas cap and summer driving with the windows down...one very 'high' girl! Had to stop on trips over a 1/2 hour and air myself out. Took about a week to discover where the gas smell was coming from.
Replaced the vented cap with a non-vented cap and the problem disappeared.
Heid

 

[huladick]

Ok, I like gas, but don't want to smell like it. Guess I'll go with the non-vented. Thanks everyone for the input.

 

[Jeffro]

I had a really bad answer earlier. I read somewhere that 70' LT1's came needed a vented cap. I believe it had something to to with the single fuel line to the engine. Does anyone have info on this?

I currently have a vented cap and I am all to familar with the fume problems.

J

 

[DDLS3]

Jeffro,
On all corvette models to 1972 the fuel tanks are vented to the atmosphere with a vented anti-surge type filler cap. Later models with evaprotive emission control systems use a non-vented filler cap. There are several posssible sources of the fuel smell. If your cap is old it may be leaking fuel when the tank is full around the filler area everytime you accelerate a bit and force fuel out or the anti-surge valve assembly may be shot. Check around your carbuerator for leaks at the throttle shaft and fittings that may be dripping onto the intake manifold. Look at your fuel lines around the fuel pump and the pump itself for cracks or leaks. These are best checked with the engine running and the lines under pressure.

 

[Brettmc]

Fumes

I bought an original type non-vented cap for my 74 in order to fight a gas fume smell while driving and in the garage after it was parked. Didn't help. What did help was plugging the line that ran from the tank to the engine compartment. I guess it was the evap. emission line before Bubba "fixed" it. At that point tho, the tank was not vented. You can imagine how my carb liked that! I then put a vented cap on it and viola!! no more fume smell!!

 

[tonyk72]

now I'm confused

I've been searching for a locking fuel cap for my '72 and finally picled one up at a Corvette savage yard for $25. The guy told me that after 69 (I think) all vettes came with vented fuel caps. I came home, looked at my original gas cap and it said (right on the cap) SEALED. Does this mean that the cap is non-vented? I then flipped through some parts catalogs like ZIP and they sold 63-74 vented locking gas caps (they are sold out though). Doc Rebuild, The Last Detail & Ecklers had 70-74 (non-locking) NOT vented caps.

So which is it for '72, vented or nonvented, and does it matter if its and LT1?

 

[JohnZ]

Not familiar with C3 specs in detail, but if your car has a tank vent line that goes to a charcoal evaporative emission canister, it uses a sealed gas cap. If it doesn't have a vent line, it uses a vented cap.

 

[bg725]

C1 gas fumes

Just started driving my 62 with the top up and noticed a strong gas smell while driving. Anyone have any ideas? Vented or nonvented cap?

 

[6880 Mike]

Sorry, but this thread is eleven years old and concerns C3s. You want the C1-C2 Forum.

 

[AussieDoug]

I'm pretty sure it needs to be vented. The only unvented caps I have ever heard of from the factory were on 70 LT1's and they were quickly replaced due to problems.

J

My 72 has the carbon canister and vent valve setup. Will be replacing it as it causes problems when tank is filled