Technical 53 Chevy Belair fuel issue

1953 Chevy Belair
305/350 combo
mechanical fuel pump
quadrajet carb

it seems as though every time I get down to 3/8 tank of gas I start to get what seems like fuel starvation on steep hills and heavy acceleration, getting worse as fuel level gets lower.
the fuel outlet is on the front bottom edge of the tank.
my question is, does anyone know if there is an internal tube in the tank that could have fallen or rotted off?
or should I be looking some where else in the system?

 

Sounds like could be a vent issue.
Tried leaving the fuel cap off?
Easy giveaway is the 'sucking' of air as you undo the cap.

 

cap jiggles when tight, no vent issue there. actually should get a new cap since when it's full it does splash a little out on hard right corners.

 

I believe that there is a pickup tube in there.

 

I go along with the pickup tube having a problem. Pinhole leak in the tube or maybe bent.

 

Cap not venting would cause it to stall as soon as the fuel pump pulls a vacuum on the tank that it can't overcome.

 

One of my high school classmates had that problem with a low fuel level and a v8 engine. If the fuel level got too low he had to back up hills. He added a hose with a short piece of brass pipe in the end for weight so it would go to the back of the tank on acceleration or up steep hills. I suppose the original 6 cylinders didn't use as much fuel so what was in the line would take them a long way. My grandfather always cautioned against putting too much gas in the 50 Chevy on the farm. He claimed it got such good mileage that you had to drain some gas out every so often.

When I thought about it, the pickup should be at the rear of the tank. Fuel isn't so critical going downhill. You can coast.

Maybe a quick fix would be to add some volume with a large filter or two.

 

another possibility is that the tank was cleaned/sealed inside at one time - if so, sealer can come loose and partially block pick up tube upon acceleration, etc

 

Thank you everyone for the great reply's.
I'm thinking it is a fuel pickup issue due to the fact that the bogging seems to get worse at lower levels of fuel in the tank.
I just filled up so it'll be a bit till I drain the tank to check it out, it won't be long since my 53 is my daily driver .
I will post up my findings here.
Jalopy Joker - I do like the idea of an active fuel pickup that you mentioned