Which gas cap do I need for my car? Vented or non-vented?

1970 Coronet, does NOT have California emissions package.

For a non-ECS car I'm going to say vented.

http://www.allpar.com/fix/fuel/evaporation-control.html

I ain't for sure if this applies but does it have the mini vent hard line attached to the filler neck inside the trunk? I would think with that, that you would not want extra venting in the cap???

vented

Besides being vented or not....
Note that in 1970 Dodge and Plymouth used (2) caps with different size tabs. 1 had narrow tabs for the cam and 1 had wider cams....

Just my $0.02...

Narrow tab, vented.

The vented ones will at least not let your tank form vaccum inside from fuel withdrawl if the tank vent lines ever get plugged. On my car, someone put in the wrong year fuel tank and plugged all the vents hoses. I had to put on a vented cap because my tank would suck shut while driving.

My here. I thought the B-bodies with their flat tanks and filler necks behind the license plate used non-vented caps. That is the reason there is a vent line that goes from the tank, up through trunk floor, up wheel well and back out. The vent line forms a gas trap that ensures proper gas path. I recall reading that vented caps could expel fuel from a slug of fuel sloshing against the cap on hard acceleration. I always make sure the vent is clear and have always used non-vented caps. Never had an issue.

I think e-bodies and chargers where the filler neck is far above fuel level used vented caps (depending on ECS requirements).

Anyone have a parts book or manual handy?

Well, here's the one I bought. http://www.classicindustries.com/product/mopar/parts/st10632.html

I'm hoping it's the correct unit and that the picture is wrong (says "non vented") I didn't notice till After the purchase. The cam may not be right either. I guess I'll see. Thanks for the advice, gents. It's crazy the basic questions you need to ask when your car came to you in boxes and half the parts missing.

GAHHH! Wrong one. Got the non vent type. Guess I'll see if the cams fit. Rats.

You got the correct one. Non Vented fits your Bee. If you installed a new tank, make sure the vent lines are hooked up to the correct tank nipples. The Spectra Premium tank I installed in my '70 Bee had the vent nipples reversed. The long line in the tank that goes all the way to the back connects to the short vent line clipped to the crossbrace above tank, and the short line nipple connects to the vent line that passes up into the trunk.

I got both vent lines connected but did it over a year ago and can't recall which one I connected to which hose. I know I consulted the FSM. But in the end I think I connected the one closest to the hole for the trunk tube to that tube. I'll get under and check.

As long as it's the original tank you won't have any problems. It's the aftermarket you have to be careful with. You can see the vent lines from the filler tube opening.