Fuel Filter only about 50% full

[semaj4712]

Quick question. On my wife's 66 c10, she has this inline fuel filter pre pump. It only is ever about 50% full even when running.

I would think it should be more full than this, and obviously, there is an air pocket in it but I cannot seem to get rid of it.

I have done some searching around and cannot find much info on the filter being pre pump like this.

It does not seem to affect the engine idling or giving it gas, we have not driven it yet as this is a rebuilt motor going back in and I still have a laundry list of things to do to get it all finished up.