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10-07-2009, 08:32 PM | #1 |
Just a car guy
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Location: New Washington, IN
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Gas tank vent?
Background. Truck is a 1969 250 6cyl 3 speed, original. Original tank.
The paint was gone under the gas filler when I got the truck. Figured it was from people overfilling, but learned the the gas cap was not sealing and gas would run out of tank when making hard right turns. Went to OReillys and got a new cap. It sealed much better, and gas no longer leaks. Now, when ever I take the cap off, there is a major whoosh sound and sometime you here the tank pop, like its getting sucked in. So, I guess the tank is no longer venting. Did they give me the wrong cap? Is there a vent somewhere else that I need to check for?
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
10-07-2009, 08:38 PM | #2 |
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Re: Gas tank vent?
they gave you the wrong cap// you need a vented tank cap. the cap you have is correct for the later 71-72trucks
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10-07-2009, 08:39 PM | #3 |
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Re: Gas tank vent?
thanks!
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
10-23-2009, 11:38 AM | #4 |
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Re: Gas tank vent?
Well I double chacked it.
Got the right gas cap. It is vented. I looked at the tank in the truck and do not see a vent. I have been putting the cap on, and not tightening it all the way. FWIW, I checked 2 different parts stores, looked a 4 or 5 different caps.
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
10-23-2009, 03:02 PM | #5 |
The Older Generation
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Re: Gas tank vent?
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Are you going by the box or does it say vented on the cap? I would try another brand of vented cap. I would say the cap has to be mis-labeled or defective. LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - Last edited by LockDoc; 10-23-2009 at 03:03 PM. |
10-26-2009, 11:54 PM | #6 |
70 Chevrolet=Obsession
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Re: Gas tank vent?
Lockdoc is right. The cap can't be vented and create a vacuum in the tank. The cap is wrong or it is defective. period.
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I'm Just like my truck. Old, Ugly and Grouchy. Except my truck starts easily in the morning and doesn't smoke! IT'S NOT EASY BEING GREEN! -Kermit the frog 1970 Chevrolet C-10 Longbed Stepside : 350, Muncie M20, 3.08 GM corp. positraction Forest green exterior/light green interior(Where all my money goes) 1996 Toyota Corolla (Parts runner) |
10-26-2009, 09:53 PM | #7 |
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Re: Gas tank vent?
I looked at the cap. Looked up models for 70 and 72 and compared mine to ones from auto zone and oriellys
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
10-29-2009, 07:43 PM | #8 |
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Re: Gas tank vent?
Well,
I went to Auto ZOne and bought another cap(first one came from oriells) Still doing the same thing. ?????????????????????
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
10-30-2009, 05:50 AM | #9 |
70 Chevrolet=Obsession
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Re: Gas tank vent?
This doesn't make sense. If the cap is vented then it can't create a vacuum. The only conclusion I can come to is that the new cap you bought isn't a vented cap. Maybe it's the wrong cap and somehow it's prevented from venting because of the way it fits on the neck of the tank.
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I'm Just like my truck. Old, Ugly and Grouchy. Except my truck starts easily in the morning and doesn't smoke! IT'S NOT EASY BEING GREEN! -Kermit the frog 1970 Chevrolet C-10 Longbed Stepside : 350, Muncie M20, 3.08 GM corp. positraction Forest green exterior/light green interior(Where all my money goes) 1996 Toyota Corolla (Parts runner) |
10-30-2009, 09:13 AM | #10 |
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Re: Gas tank vent?
You're telling me. I just finished building a 455 Olds for a guy, yet I can't seem to get my gas cap on right!
This is the cap, http://www.autozone.com/autozone/cat...questid=197231 Looks just like the first one I got from Oriellys as well.
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
11-01-2009, 12:12 PM | #11 |
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Re: Gas tank vent?
hey OJ1988,
did your figure anything out yet, I just bought a new vented cap and am having the same issue, never happend with the old cap, I was wondering if gas had sloshed into the vent after I filled up and plugged the vents, anyway I put the old cap on and let the new one dry out and am gonna try it out today and see what happens, kinda wierd |
11-01-2009, 01:23 PM | #12 |
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Location: Lambertville MI
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Re: Gas tank vent?
whats wrong with not having a vented cap.. i bought my truck with a non vented one and i hear the same noise when i take off my cap. is there anything wrong with that?
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11-01-2009, 01:53 PM | #13 |
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Re: Gas tank vent?
If the fuel pump pulls enough vac on the tank it will collapse the rubber fuel lines and you will not get gas to the carb.
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11-01-2009, 01:36 PM | #14 |
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Re: Gas tank vent?
creating a vacumn in the tank means now your fuel pump has to work harder to pull fuel.
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11-01-2009, 01:41 PM | #15 |
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Re: Gas tank vent?
would i notice any differance if its vented or non vented
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11-01-2009, 01:46 PM | #16 |
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Re: Gas tank vent?
yea, the sound will go away.
and you may have to replace a fuel pump a lil sooner. you have to have a vented cap on a non-vented tank.
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11-10-2009, 10:36 PM | #17 |
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Re: Gas tank vent?
Well, maybe the parts suppliers got a bad batch of caps? I've tried 3, and another guy here having the same problem.
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1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig |
11-11-2009, 08:24 AM | #18 |
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Re: Gas tank vent?
You can check the cap buy sucking on the hole on the under side. You should be able to suck air through it but not blow through it
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