What is an "anti surge" gas cap?

[brads70]

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&rd=1&item=110357662902&ssPageName=STRK:MEWA:IT&ih=001

Looks a little "rich" for a gas cap???
I have a 70 challenger , do I need to use this cap? Or can I get away with a cheap one from a jobber? I don't care much about #'s matching. I was going to order a flip gas cap from them.

[Chryco Psycho]

you can get away with any small cap that will fit under the flip cap , the 70 was externally vented so even the cap doesn`t need to be vented

[brads70]

Thanks again! I asked before on here somewhere about the extra tube that is the same size as the fuel filler tube in the trunk, Found out it's part of the evaporation control for CA cars? Is this how it's vented? I ask because it has 4 tubes plugged at the tank that go ( I assume) to this tube in the trunk that has 4 holes also plugged. Do I need to connect them in order for the tank to vent?
Thanks Brad

[RT Dude]

Hey Brad.
My Challenger is a 440 R/T LA car, so i think the fuel setup is the same as mine.
Im trying to post the pics, but it says the upload folder is full. 

[RT Dude]

OK. Try again.

[brads70]

Yep That's it. Except I think mine comes out at the back of the tank ( I think? )