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gas cap

Old 10-22-2018, 05:17 PM
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egerson
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Default gas cap

C1 - 1958
still working on gas smell.
is the gas cap supposed to be VENTED or UNVENTED?
thanks
E g
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Old 10-22-2018, 05:21 PM
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Frankie the Fink
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NON- Vented.
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Old 10-22-2018, 05:40 PM
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egerson
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Eckler's is selling an "OEM" cap for the C1 and shows it is VENTED.
confused...

Corvette Gas Cap, 1953-1962

1953-62 (C1) Gas Cap

Part #:25-120566-1Replacement for OE #: 14002439 Alt Part #: A2376

Fitment:
1953 thru 1962
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Old 10-22-2018, 05:56 PM
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JohnZ
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Originally Posted by egerson View Post
Eckler's is selling an "OEM" cap for the C1 and shows it is VENTED.
confused...

Corvette Gas Cap, 1953-1962

1953-62 (C1) Gas Cap

Part #:25-120566-1Replacement for OE #: 14002439 Alt Part #: A2376

Fitment:
1953 thru 1962
Eckler's is WRONG-WRONG-WRONG, as usual; they should stick to jewelry and T-shirts. C1's use NON-VENTED gas caps, period.


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Old 10-22-2018, 06:14 PM
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thanks but how do you REALLY feel about Eckler. You sound ambivalent.... LOL
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Old 10-22-2018, 08:53 PM
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Default Vented or Non Vented - That is the question

I believe all gas caps of that era are vented. Modern replacements for these Corvettes have an anti surge capability to prevent fuel spills in the event of an accident. There is no other vent for the gas tank, so eventually you pull a vacuum and no more fuel will flow to the engine with a non vented cap. Non vented caps were not introduced until much later and required other means for venting the fuel tank.
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Old 10-22-2018, 08:57 PM
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Originally Posted by firemist1 View Post
I believe all gas caps of that era are vented. Modern replacements for these Corvettes have an anti surge capability to prevent fuel spills in the event of an accident. There is no other vent for the gas tank, so eventually you pull a vacuum and no more fuel will flow to the engine with a non vented cap. Non vented caps were not introduced until much later and required other means for venting the fuel tank.
I am sorry but you are wrong, C1s vented the gas tank NOT the cap.

Last edited by 68hemi; 10-22-2018 at 08:58 PM.
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Old 10-22-2018, 09:06 PM
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Originally Posted by firemist1 View Post
I believe all gas caps of that era are vented. Modern replacements for these Corvettes have an anti surge capability to prevent fuel spills in the event of an accident. There is no other vent for the gas tank, so eventually you pull a vacuum and no more fuel will flow to the engine with a non vented cap. Non vented caps were not introduced until much later and required other means for venting the fuel tank.
You must have overlooked JohnZ's post above.
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Old 10-22-2018, 09:15 PM
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You are correct. I checked the schematic diagram for the '58 and it does show a separate vent hose for the tank (I should have done that first!). Sorry for the incorrect information.
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Old 10-23-2018, 12:17 AM
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If you have a vented cap and want a non-vented cap, you can use a small blob of JB Weld to seal the vent hole.
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Old 10-23-2018, 07:55 AM
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Having said all that and acknowledging a vented cap is incorrect for C1s - the cap is prob not the source of your gas smell (unless the gasket is shot)l any more than your already "open to the atmosphere" tank vent hose.

A disadvantage of the open hose (at least on my 61) was in making hard right turns, particularly uphill, with a topped off tank. Raw gas would run out the vent tube and I would smell it after the maneuver. To wit, avoid completely topping off the tank.

Last edited by Frankie the Fink; 10-23-2018 at 08:03 AM.
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Old 10-23-2018, 09:04 AM
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Originally Posted by SDVette View Post
If you have a vented cap and want a non-vented cap, you can use a small blob of JB Weld to seal the vent hole.
I put the 'right sized' SS sheetmetal screw, with JB Weld on the threads, into the vent hole in the underside of the cap
Bill
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Old 10-23-2018, 12:00 PM
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OK, I get it, now. Since there is a vent TUBE, the cap does not NEED to be vented to avoid "pulling a vacuum."
I took the cover off the gas tank (in the soft top compartment behind the seat) and can see the vent tube which crosses over the top of the tank & ends right next to the gas cap.
I tested the vent tube, and it allows air flow easily.

So here is my next question.
If a vented gas cap AND the vent tube BOTH vent into the gas filler area, other than being "purist", I see no problem having TWO VENT SOURCES.
I see how having NO VENT, neither a vent tube nor a vented cap, would be a problem - i.e. pulling a vacuum - , but I can't see why having a VENTED cap & a VENT TUBE would ever be a problem.

Am I missing something having to do the physics of venting???
thanks
ED G
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Old 10-23-2018, 12:11 PM
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I think your logic is sound Ed G... and like Frankie said, it takes a lot to actually vent from the cap vent..
But it is one more place for gas stink to come from.....
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Old 10-23-2018, 12:21 PM
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Originally Posted by egerson View Post
OK, I get it, now. Since there is a vent TUBE, the cap does not NEED to be vented to avoid "pulling a vacuum."
I took the cover off the gas tank (in the soft top compartment behind the seat) and can see the vent tube which crosses over the top of the tank & ends right next to the gas cap.
I tested the vent tube, and it allows air flow easily.

So here is my next question.
If a vented gas cap AND the vent tube BOTH vent into the gas filler area, other than being "purist", I see no problem having TWO VENT SOURCES.
I see how having NO VENT, neither a vent tube nor a vented cap, would be a problem - i.e. pulling a vacuum - , but I can't see why having a VENTED cap & a VENT TUBE would ever be a problem.

Am I missing something having to do the physics of venting???
thanks
ED G
If you're trying to rationalize buying a vented cap instead of a correct one you've succeeded....

Your initial post asked what is correct ? Now this has morphed into what will work....

But JohnZ doesn't want you to be misled by what the vendors offer up......like gaskets under the midyear door locks (that the factory never used) there are some things they try to sell that are flat out wrong...

Last edited by Frankie the Fink; 10-23-2018 at 12:22 PM.
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Old 10-23-2018, 12:37 PM
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Originally Posted by Frankie the Fink View Post
Having said all that and acknowledging a vented cap is incorrect for C1s - the cap is prob not the source of your gas smell (unless the gasket is shot)l any more than your already "open to the atmosphere" tank vent hose.

A disadvantage of the open hose (at least on my 61) was in making hard right turns, particularly uphill, with a topped off tank. Raw gas would run out the vent tube and I would smell it after the maneuver. To wit, avoid completely topping off the tank.
Frankie,
I have the same problem with my 57 and I an going to plug the vent tube and use a vented gas cap to see if it will help.
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Old 10-23-2018, 01:17 PM
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Originally Posted by 68hemi View Post
Frankie,
I have the same problem with my 57 and I an going to plug the vent tube and use a vented gas cap to see if it will help.
it's just as easy to slosh out the vented cap as the vent from the tank; maybe easier as there is a larger possible quantity and an almost level passageway from cap to tank. remember, when it vents from the cap it vents into the filler compartment which is just about nose level. you can try to fit the tank vent hose down the drain hose which will get the smell farther away from you

best plan, don't overfill the tank (but I overfill mine all the time and don't have the 'smell')
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Old 10-23-2018, 01:56 PM
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Originally Posted by wmf62 View Post
it's just as easy to slosh out the vented cap as the vent from the tank; maybe easier as there is a larger possible quantity and an almost level passageway from cap to tank. remember, when it vents from the cap it vents into the filler compartment which is just about nose level. you can try to fit the tank vent hose down the drain hose which will get the smell farther away from you

best plan, don't overfill the tank (but I overfill mine all the time and don't have the 'smell')
Bill
When my car was restored 25 years ago they put a new fuel tank in it and I can only get about 13 gallons in the tank when it is bone dry empty so I don't get much range with a 383 stroker engine. I will try to fit the tank vent hose down the drain hose. Thanks.
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Old 10-23-2018, 02:18 PM
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Modern vented caps and I think even the midyears have a one way valve in the cap. Air is drawn in to stabilize tank pressure as gas is consumed and vacuum created. Then the valve closes. To wit, there shouldn’t be any fuel sloshing out of the cap. I don’t recall if the C1 repro caps have the valve but a suck and blow test will tell for sure.
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Old 10-23-2018, 02:22 PM
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If you’re really concerned about the smell, go buy a fuel filter with 3/8” nipples that unscrews so you can replace or clean the filter. Then buy some granulated charcoal meant for fish tanks from your local pet shop (Petsmart, whatever). Fill the filter with the charcoal and connect it to the end of your tank vent hose with the filter screen closer to the fuel tank and put another length of hose on the other end and direct it away from the passenger compartment. You will never smell gas from the vent again.
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