1932 Pontiac Six build

[Rattiac]

Let's talk gas caps.
I was talking with someone earlier about why my car isn't running (fuel pump) and he said I should look at my gas cap cause it probably isn't vented.
He couldn't find one for his car (same year) and had to drill a small hole to vent it.

I have noticed when I get a tank of gas and remove the cap I get a quick sucking hiss.
With a full tank it pushed air out when cap removed.

Hmmm something to ponder.
He did try to talk me out of going to electric pump.

[sixball]

With old cars it's like the crank case breather. They vented out into the world and caused climate change. Now they capture  the dangerous emissions from the crankcase and fuel tank and run it back through the engine and the when it comes out the exhaust somehow it is cleaner. Anyway old gas caps were vented so outside air could fill the space created as the fuel is used.

[62131]

Over filling your fuel tank will keep it from venting  properly 

[sammons]

Yep, non-vented gas cap on oldies is a no-no. Creates a vacuum as the fuel is used that makes it hard for the pump to over come.
   My brother helped his buddy move to Calif, he drove his Vette and buddy drove his '53 GMC p.u.. About a 1/4 tank used it would quit running, non vented cap. Brother pulled cap, stuffed a rag in till next town and got a vented cap😁

I can't remember which make, but they went to a non vent cap but ran a breather line (kinda like a return line) up with a breather type cap. Later it ran to the emmision charcole canister and to carb. Think Mopar ran a breather line up in the trunk, it made a loop up high, then back thru floor and into the frame rail to vent.
   
I've always ran mechanical, but on a few I plumbed in an electric as a back up or to get pressure up after one sat for a long time.

[chopper526]

On my '32 I used a vented tank with a non vented cap, but 100%, you have to vent the tank somehow.

[Rattiac]

Well heres my cap. I think its vented. 
The package didnt say .

[TFoch]

I blocked the vent on top of my tank because I couldn't route it higher that my filler neck.  Then I used a vented cap.  It may taste like gas but you should be able to blow into those holes and check to see if it is vented.

[sixball]

What else would the holes be for?

[Rattiac]

I pulled off the cap,  cleaned it off and blew into it and nothing  .
If it is vented I wonder how much psi it takes. 
Tried a few times.

[chopper526]

I do believe that is a vented cap. My cap is a solid piece of aluminum, my tank is vented. I ran a piece of rubber hose straight up and put a "L" curve in the line to keep dirt out.

[62131]

Tanks must be vented; be careful in selecting your vented cap if it is not correct for you tank neck it can fit to tight and crush the gasket and cut off the air supply 

[Rattiac]

Just ordered a gas cap from The Filling Station. 

Wait..... theres some irony there. 😄

[Rattiac]

New cap came.  Compared it with the old one.  Pretty similar.
Well at least I know the cap is right.

Probably start looking into a fuel pressure regulator soon.

[Rattiac]

Kinda forcing myself into this.  Went to metal-mart and picked up a stick of 1-1/4" square tubing,  had it cut in half.  $45 .
Should have enough for the 2 top pieces and a few vertical pieces. Just need to figure out how I'll brace it all and not be in the way when I install the uppers.
Have some 1" square left over for that.

Probably start the car up today and pull it out to prep/clean the work area.  Maybe a short drive.

[chopper526]

I think it is going to work out well for you. I had zero experience when I did my car and it worked out great for me.