My 69 won't start with under 16 gallons- help!

[CaliGal]

Hi Alex

I hadn't thought of the line heating. Thanks!

Here's an update:

Running while less than full was apparently a one-time event (a trip to San Diego). At home, I let it idle until the fuel ran below about 16 gallons, and this time she stalled out-- exactly as if running out of gas. It's like the car only has a 4 gallon tank. When it gets close, I can't rev to hard or there's a cough.

The line does run very close to the manifold (an Edelbrock 4), but since she won't start cold with under 16, I'm guessing that's not it. The new circumstances seem to reintroduce the possibility of something in the tank. Any more ideas or should I just drop it and look for a prize inside?