Gas Cap/Hot tightly sealed???

[Banky]

Hi all,

I'm almost ready to fire up my 30! Question. How tightly sealed should the gas cap be? Does it need to breath? Mine is pretty loose, so much so that I think it's going to rattle while driving. However I'm sure there will be lots of rattles, Ha Ha. I was thinking about cutting a new rubber or cork circle to fit around the edge. But I don't want pressure to build up and blow something out. Had that happen to me with a new plastic gas tank on a 54 chevy once. I didn't have the proper vented cap one, was lots of fun!

Any thoughts from the pros?

thanks,
Banky