Sealed vs. vented gas cap
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
This is what I have found with my vette. I bought a sealed gas tank lid for mine when I first got the car. All was fine with the car. After I rebuilt the motor, I put on an Edlebrock Fuel pump and eliminated the return line to the tank. Now, if I fill the tank and run most of it out in one day, when I loosen the gas cap, I can hear the tank sucking in air.
Deducing from that, I would think that vented would be the way to go. I am still running the non vented style on mine though.
Maybe someone else that knows a little more will chime in on this one.
Deducing from that, I would think that vented would be the way to go. I am still running the non vented style on mine though.
Maybe someone else that knows a little more will chime in on this one.
Drifting
Joined: Dec 2004
Posts: 1,345
Likes: 3
If you run a non vented cap and use a fuel return line your tank will pressurize. The '69 owner's manual warned you to open the cap slowly to relieve any pressure. If you do not run a return line you could draw a vacuum in the tank, although when I ran this way I never saw any sign of that happening.
You may smell gas if you use a vented cap.
You may smell gas if you use a vented cap.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I am running a non vented cap and have no return line. I have never had any problems running this way. My car did not come with a return line. It did have the charcol cannister which I have eliminated. I just plugged the line from the tank.
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
But hes got a 72 and should have a sealed?
My 68 wouldn't matter sealed or vented since the overflow would let the air in anyway. I found this out from too much gas and too much acceleration
My 68 wouldn't matter sealed or vented since the overflow would let the air in anyway. I found this out from too much gas and too much acceleration
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Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
Unless the 72 is an LT-1, then it should have EEC (vent to canister)
on the drivers side of the tank. You should be able to see this,
looking up under the fender. With the vent (properly working),
it should use a sealed cap. Without the vent, use a vented cap.
I chose to block my vent line at the tank and use a vented cap.
OK - looking further, maybe even 72 LT-1s had EEC system.
Yup - just looked it up - all 71,72 have EEC system.
The LT-1s do not have a return fuel line from the pump.
on the drivers side of the tank. You should be able to see this,
looking up under the fender. With the vent (properly working),
it should use a sealed cap. Without the vent, use a vented cap.
I chose to block my vent line at the tank and use a vented cap.
OK - looking further, maybe even 72 LT-1s had EEC system.
Yup - just looked it up - all 71,72 have EEC system.
The LT-1s do not have a return fuel line from the pump.
Last edited by NHvette; Aug 9, 2005 at 10:08 AM.
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Originally Posted by DonBecker
I'm having bad stall issues, 76, L-48 w/vented cap...GDaina, more info please?
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Originally Posted by DonBecker
Cool. But how would putting a vented cap on an originally non-vented cap car cause an issue? Would it?
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
The non-vented caps were added as an evaporative emissions HC control. Cars with non-vented caps used a charcoal cannister to absorb the fuel vapors. The vapors are purged after the engine is started and the fumes burned similar to how the PCV system works. A solenoid valve is usually used to purge the vapors.
Using a vented cap on a car that was intended for a non-vented cap won't hurt anything other than you will smell gasoline vapors occasionally. It can also be a quick fix for a faulty purge system.
Putting a non-vented cap on a car that was meant for a vented cap can problems such as fuel starvation or in GDAINA's case, worse.
Using a vented cap on a car that was intended for a non-vented cap won't hurt anything other than you will smell gasoline vapors occasionally. It can also be a quick fix for a faulty purge system.
Putting a non-vented cap on a car that was meant for a vented cap can problems such as fuel starvation or in GDAINA's case, worse.
Team Owner
Joined: Jul 2004
Posts: 40,380
Likes: 788
From: Redondo Beach, California
Put on a vented cap. This will make everything easier for fuel flow. There may be some esoteric issues with gasoline vapor escaping into the air, but I think if you do this the world will not be really effected.
I have vented caps on my 68 and 70 and as far as I know there's been no adverse effect on the environment.
I have vented caps on my 68 and 70 and as far as I know there's been no adverse effect on the environment.
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Originally Posted by 68/70Vette
Put on a vented cap. This will make everything easier for fuel flow. There may be some esoteric issues with gasoline vapor escaping into the air, but I think if you do this the world will not be really effected.
I have vented caps on my 68 and 70 and as far as I know there's been no adverse effect on the environment.
I have vented caps on my 68 and 70 and as far as I know there's been no adverse effect on the environment.
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
fuel vapor extremely flammable...how many times have I've seen on the news a story about a car catching on fire as the driver is filling the gas tank...static electricity igniting the fuel vapors.
Not something I want to mess with...use the correct cap for the system the cap is designed for.
Not something I want to mess with...use the correct cap for the system the cap is designed for.
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
my '68 originally came with a vented cap which I'm still using.. However, I changed my gas tank and went with a tank that doesn't have a return-line hook up... Don't know if the vented cap is the right cap for that setup, but I believe it is because I've never had any issues...
