Gas tank vent?

I've got a spun aluminum tank that I want to use for a gas tank. I have a filler neck and a spin on knock off style car for it. Any ideas for the best way to vent the tank?

If this post gets repeated, sorry. My first post here.

Thanks, Dan

 

usually the cap is the vent

 

my name is? nice intro SLIM SHADY

 

Any more input on this?

 

you may have drill the cap and put a check valve like they use in fuel cells on the dirt trackers or find a spinner thats vented. i have made some strange tanks for my demo derby cars