starting problem after sitting 1947

[cabrioletgalaxie]

So after cleaning my carb and finding a sliver of metal in the gross jet the car would start and run well. Turned it off and started it half hour later and it ran fine.
Tried starting it after letting it sit for about a week it took a long time to fire. I had to crank it over several times with the choke in different positions. It seemed there wasn't enough gas to start it.
I am wondering if there is a situation where the gas might drain itself from the bowl after sitting for a number of days. Is this a common problem?
History: The fuel pump was replaced 2 weeks ago, carb rebuilt last year, new gas tank last year.
Thanks.