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1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

Venting issues

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Old Jan 31, 2026 | 02:43 PM
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Venting issues

I have ordered a vented gas cap for my 1967 Ford f100 in cab tank two times and continue to get the non-vented cap. The sales people at LMC truck are unhelpful in that they cannot determine what part number I need. Can anybody help me with this with a correct part number?
 
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Old Jan 31, 2026 | 03:55 PM
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Don't use LMC. Just visit your local auto parts store like NAPA:
https://www.napaonline.com/en/p/THM7031220
 
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Old Feb 2, 2026 | 01:15 PM
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Originally Posted by David7
I have ordered a vented gas cap for my 1967 Ford f100 in cab tank two times and continue to get the non-vented cap. The sales people at LMC truck are unhelpful in that they cannot determine what part number I need. Can anybody help me with this with a correct part number?
The cap on the right is an original vented cap. The one on the left is what you will get from about any parts house, it isn't vented. But if you drill a 1/16-hole thru the center of the check valve it will work just like the original.

 
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Old Feb 4, 2026 | 11:45 AM
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The cap above with the red valve is called a pressure-vacuum cap. It allows air into the tank but does not allow gas vapors to escape. It replaces all vented caps and should work fine
 
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Old Feb 5, 2026 | 05:33 AM
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Originally Posted by davelj
The cap above with the red valve is called a pressure-vacuum cap. It allows air into the tank but does not allow gas vapors to escape. It replaces all vented caps and should work fine
Sorry but it won't work unless the truck has a vapor recovery system. The tanks without a vapor recovery system will build pressure when parked especially on a hot day.
 
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Old Feb 9, 2026 | 01:06 PM
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I got a vented cap from Carolina Classics that was actually vented. No more coming home to fuel pouring out of the cab because it pushes past the fittings under pressure!

https://carolina-classics.com/collec...1-b7c-9080-kit
 
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Old Feb 9, 2026 | 10:43 PM
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Originally Posted by bszern
I got a vented cap from Carolina Classics that was actually vented. No more coming home to fuel pouring out of the cab because it pushes past the fittings under pressure!

https://carolina-classics.com/collec...1-b7c-9080-kit
Interesting the vented cap from Carolina Classics looks just like the cap above that Crop Duster says isn't vented, just has a different color valve.

 

Last edited by 52 Merc; Feb 9, 2026 at 10:45 PM.
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Old Feb 11, 2026 | 09:19 AM
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Originally Posted by 52 Merc
Interesting the vented cap from Carolina Classics looks just like the cap above that Crop Duster says isn't vented, just has a different color valve.

Yeah, I'm not sure if the blue vs red means anything here. I did the breathing test (blow and suck through the cap) and it worked. I tried 3 different "vented" options that were only 1-way vents for vacuum relief before I got this one. It's been working for a year now, so I'm happy.

The alternative is to just crack the cap open a little bit when parking so it can depressurize, my step-father does that with his custom engraved cap for his 1931 Model A that isn't vented 2 ways.
 
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Old Feb 12, 2026 | 07:05 AM
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I think I would drill a small hole in the cap
The original vented cap had no check valve, same as the old GM stuff like my Camaro
Take off quick in a Camaro and you leave a small trail of fuel
That's the fuse
 
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