Vented or Non-vented gas cap???

[igasper10]

What are the pros & cons of having a vented gas cap over a non-vented one?

ian

 

[Eric]

It all depends on if your tank is vented. If your tank is vented, there really is no purpose in a vented cap that I can think of. If your tank is not vented, you have to have some way to ventilate the tank or you will suffer from vapor lock on some nice sunny day when the temp hits 95 and you're sitting at a light and can't figure out why your car is dead.

 

[DDLS3]

According to the Corvette Shop Manual the 72 was the last model year to vent the gas tank to atmosphere via the gas cap. All subsquent model years came from the factory with evaporative emmisions systems and a non-vented cap.

 

[Vettehead Mikey]

It's not a case of one being 'better' than the other. Your system was designed to work properly either with one or the other.

In the case of pollution controlled Vettes like your '74, you should have a non-vented cap. To use a vented cap defeats the purpose of the charcoal canister. Very Bubba!:J

 

[74bigblock]

I concur after replacing the tank, filler neck, cap and sending unit in my 74. There is a vapor line that runs from the drivers side on the tank, up to the charcoal cannister in the drivers front fender well. You need to check and make sure you have a stock tank and vent. If you do... get a non vent cap... if there is no vent line on drivers side.. then get a vent cap.