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.

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, 20241 yr by Frosty

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

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.