Non-vented vs Vented gas cap for late 50's early 60's Pontiac

[Rick Pumphrey]

Question about Non-vented vs Vented gas cap for late 50's early 60's Pontiacs.

If my car sits for more than a day, it is hard to start; sometimes taking  4 or 5 tries at starting.  The car has a Non-vented gas cap on it...(1960 Pontiac). I always thought these cars were supposed to have Vented caps. I'm thinking it may be causing a vacuum effect in the gas tank, causing it to be harder to draw the fuel to the motor. So the question is:

What type gas cap are you all using on your late 50's/early 60's Pontiacs? Do I need to switch to a Vented gas cap? Thanks for the help.

[Frosty]

GM used both vented and non-vented gas caps over the years.

If you car has a charcoal evap cannister in the engine compartment - usually on the passenger side of the engine bay, then you can run a non-vented cap. Otherwise you should be running a vented gas cap to insure that you won't have fuel delivery issues.

 

Charcoal evap cannister looks something like this in the engine bay.

Edited September 11 by Frosty

[Rick Pumphrey]

Thanks Frosty,

That's what I kind of thought. It currently has a Non-vented cap. There is no charcoal canister that I see. So, I will try a Vented cap and see if that helps. Thanks again, Rick

[Fitzy]

Rick, if there's vacuum being created in the tank, you'll hear air escaping as you undo the cap. A quick fix is to drill a couple of holes (if the cap isn't a valuable original one) that are staggered to prevent dirt ingress. I run a non vented cap in my '65 AND I rerouted the rubber vent hose so that it exits behind a rear wheel (with some fine mesh over the opening) - that way the movement of the vehicle draws away any fuel fumes. Before I did that, I could smell fuel as I drove because the fumes were accumulating in the trunk and had nowhere to go.