Gas mileage

Hi all,
My Sebring has a Chevy 350 with Holley carb and I am getting terrible gas mileage, 11-12 MPG.  I have checked floats, jets are .065", I tuned it for highest possible vacuum and checked accelerator pump adjustment, all seems normal.  

Also I have what I believe is a Chevette Gas tank and the old lines for the charcoal canister are plugged and the tank does build up some pressure, causing a gas smell. Has anyone ever installeed a canister on their tank?

Any tips will be greatly appreciated!

If I'm not mistaken, the canister has to be connected to the engine through a complicated plumbing system so that the vapors can be sucked out and burned.  You could switch to a vented cap and leaved the lines plugged, or you could route one of the smaller tank lines to a high point and use it as a vent.  I used this scheme on a street rod.  The main problem with this is that if pressure builds in a full tank, raw fuel can be pushed up the line and drip out. The vented cap would be a better solution if one is available.

As far as mileage is concerned, I can't help you with the Holley, but my car got 20 mpg with a Quadrajet and a 5 speed.

Mike