it was leakin from the filler hose up right by the gas cap and then when i opend the cap at least a gallon of gas surged out :( 2bucks of gas at least down the drive way :mad: whats wrong

Don't know about your '65, but in '69 there are two vent tubes near the top/right corner of the tank that should relieve pressure and let the tank breathe.

If someone capped off the vent, there will be two problems: 1) High pressure (possibly causing the tank to bulge or worse) if the gasoline warms up on a hot day, or 2) A vacuum causing the tank to collapse, as gasoline is drawn out but not replaced with air.

-Bob Cunningham

Sounds like Pressure, not vacuum
I don't know about 65's either but maybe you just need a new cap

65 El Caminos use a vented gas cap. Should say on the underside if it is vented. Check to see if someone has not pluged the vent tube that runs from the tank up to the top of the filler neck. This should be attached and not pluged. I think it is 3/8. Fuel line will work, with clamps on both ends.

65 El Camino 355ci. 700r4 4wheel disk brakes.
Team Chevelle Gold Member #74

thanks for the replies ill check on the lines but they didnt seem collapesed