LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Vented Gas Cap

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Old Aug 28, 2017 | 10:04 AM
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Default Vented Gas Cap

Will this vented gas cap fit my 96 z28? I deleted my evap system at the engine, and I need a vented cap now!!! I was looking for a keyed vented cap that would fit but im not finding anything.
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Old Aug 28, 2017 | 12:28 PM
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I don't know for sure, but I believe as long as it's a GM cap it should fit fine.
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Old Aug 28, 2017 | 06:54 PM
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Originally Posted by 350 groundpounder
Will this vented gas cap fit my 96 z28? I deleted my evap system at the engine, and I need a vented cap now!!! I was looking for a keyed vented cap that would fit but im not finding anything.
I didn't even think of this. I know the shop took out the EVAP system (without telling me. Didn't realize I needed a vented cap. What's the downside of not having it?
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Old Aug 28, 2017 | 10:37 PM
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Pressure build up in the gas tank. Loud hissing when opening gas cap. I imagine that can't be good on the fuel pump. I have been leaving my gas cap very slightly loose so pressure can equalize. I wonder if the shop capped off your vent tubes/charcoal canistet tubes when removing the evap system?
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Old Aug 29, 2017 | 12:04 AM
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I'll have to check. They half-assed everything. I wonder if my locking gas cap is vented. I've had it a long time. I'll check.
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Old Aug 29, 2017 | 10:27 AM
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From: Jackstandican
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If it's a Stant, like mine, then I doubt it is vented.
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Old Aug 30, 2017 | 04:31 PM
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Originally Posted by SS RRR
If it's a Stant, like mine, then I doubt it is vented.
Yeah, mine isn't either. I wish someone knew if these were the same size. Parts configurators will always say they're not compatible just because our OE is non-vented.
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Old Aug 30, 2017 | 04:34 PM
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Non vented caps required for OBD2, Why would gm even bother to build a vented one?

I prefer vent hoses that I can run though a check valve so if I get upside down there is no fuel running out.. But thats just me..
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Old Aug 30, 2017 | 04:51 PM
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From: Jackstandican
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IIRC there were a few different generations of OBDII? LT1 had one of the first generations of OBDII and I don't think it was that sensitive. I remember reading a lot of complaints from LS owners getting a DTC after not tightening the gas cap enough. Not positive, but I think a GM gas cap is pretty universal for different makes/models.

Last edited by SS RRR; Aug 30, 2017 at 05:07 PM.
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Old Aug 30, 2017 | 08:14 PM
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Originally Posted by pdxmotorhead
Non vented caps required for OBD2, Why would gm even bother to build a vented one?

I prefer vent hoses that I can run though a check valve so if I get upside down there is no fuel running out.. But thats just me..
How would you run a check valve if both the normally released pressure and the potential fuel leaking or are traveling the same way through the valve?
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Old Aug 31, 2017 | 06:52 AM
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^^^Just use a vent valve for a 3rd Gen F-Body.



The 70-74 Vettes also had a separator valve that would prevent fuel from getting into the vent line.

Last edited by MuhThugga; Aug 31, 2017 at 06:57 AM.
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