Gas Tank Vent

[Wazoo64]

I have a 67' coronet that is building up pressure in the gas tank. Need some help understanding how it vents and if I can eliminate the pressure. The car recently vapor locked on a hot day and I am thinking this has part to do with it. I just added a phenolic spacer on the carb but think the tank pressure needs to be addressed as well.
Here is some info on the car. Thanks
512 stroker
Stock tank with modified sump welded in
-8 AN fuel line
Stock fuel vent to filler neck
Non Vented Cap

 

[Wazoo64]

bump

 

[watermelon]

I use a vented gas cap on my 66. No issue here. I'm using an in tank pump and MSD Atomic fuel injection.

 

[bigmanjbmopar]

I have heard the vented cap works as well. Do you have a return line?

 

[paladin06]

Where did you get the vented cap?

I use a vented gas cap on my 66. No issue here. I'm using an in tank pump and MSD Atomic fuel injection.

 

[krowbar]

I think you already have the answer to your question in your original post. 'non vented cap' Get a vented cap and you should be golden.

 

[Chuckbizkits]

My first post! Sounds like that will solve the issue but these cars came with non vented caps. How does the ventilation system even work? The vent tube routes from the tank to the filler tube. If the tube has a non vented cap ...

 

[Dako]

The vent tube could be plugged i.e.: 'mud dauber', dead spider, etc. You may be able to work a rag down the filler neck to block anything from falling into the tank, then apply air to the vent tube where it comes out the trunk extension to try any blow it out. Or sacrifice one of those $4 Harbor Frieght blow guns with the tube on the end...by bending it to fit in from the top and try blowing out any debries from the top.

I'm with you Chuckbizkits, if it's vented to the atmosphere, then why have a vented cap?

 

[Wazoo64]

Its possible that the return line in clogged by the filler neck. I have recently replaced everything below the filler neck but did not check the return line. I am currently using the Stant 11646 cap which is non vented. I called Laysons to see if there is a vented cap for these cars and they said it should not need a vented cap. The car was designed for a non vented cap.
I am willing to try a vented cap but need a part number. I can not find a vented cap for a 1967 coronet.

 

[bigmanjbmopar]

I have a new one I couldn't use for my 69 not sure if it will fit your filler neck but you're welcome to try it for free PM me you info and I'll ship it out. It's a stant # 10640 if you want to cross check first. All I know is it would not fit my filler neck opening too small I think.

 

[watermelon]

I used a Stant gas cap Vented Style. Stant.com has make/model tool to select your car.

I filtered for 66 coronet but you can do for 67. They both have same part number.




I have 3/8 supply/return lines. I just went to Autozone and gave them Stant part number that I got off site. My cap is below

 

[67 coronet]

i had that prob on my 67.tank is vented by cap,no outside venting on tank.got a murry 6046(orielly).didnt do good at first,vent didnt seem to work good enough.took a pair of plyers and crushed the plastic vent assembly inside the cap.came right off.works great now.i live in vegas and gets real hot here,no probs so far.

 

[watermelon]

It's 7$ at pep boys

 

[BBishere2]

Laysons was wrong - the 1967 Coronet gas cap was vented - original part number 2208538, it was marked 'vented' on top of the cap.

 

[Wazoo64]

Update on this vapor lock issue I was having. The stock system was just not able to keep up with the requirements of a 600+HP 1000CFM setup. The vented cap actually has a one way check valve and that was not allowing enough air in so I drilled an 1/8 inch hole and the venting problem was solved.......However gas was returning back through the cap and running down the quarter panel.

Solution was to reroute the vent line into the trunk and cap off the vent at the filler neck. Problem solved.

 

[bigmanjbmopar]

I ended up drilling my cap out as well. 2 1/8" holes in a non vented cap and all is well, have a bit of a smell sometimes after hot days parked but no spillage on the ground like before. certainly not as much hp as you but venting the stock cap worked.

That coil in your pic looks like a still! where is the moonshine?

 

[watermelon]

Good to hear you got it worked out. 600+!!! Damn