I just changed my feul level sending unit in my 69 malibu, the new one has an extra vent line that i just plugged up. Now when i go to get gas there is a ton of pressure when you release the cap. Should I have the vent open, and if so how high above the tank would it have to be?

Sounds like you got a fuel sender with a fuel return. Just plug it. '69 Malibu tank is vented through two pipes at the right front corner of the tank which is connected to a plastic liquid/vapor separator. If any of this is plugged, you will get pressure build-up. Don't go to a vented fuel cap, you'll just loose gas out the vent on hard acceleration.

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Fred Aldrich
Web Site: www.GeoCities.com/~69_chevelle (http://www.GeoCities.com/~69_chevelle)