Auto Racing: fuel cell, fuel vapors, vent tube

Question
John, I bought a 1971 nova that had seen some drag racing
(in its past) to some degree.  It has a relatively stock 350
with a mechanical fuel pump. The fuel tank was replaced with
a fuel cell. I noticed what looks like an air conditioner
"cap/fitting" standing verticle (on top) towards the front
of the cell. I took the cap off and it seems to be open as
if it should have a hose attached to it. Is this supposed to
be a vent?  Could this be the reason the car runs badly, as
if starving for gas? Thanks for your time and input.

Answer
HI KEITH. YOU KIND OF ANSWERED YOUR OWN QUESTION. YES THE CAP IS NOT A GOOD IDEA. IF THE PUMP IS PULLING FUEL OUT THEN AIR HAS TO COME IN OR A VACCUUM IS CREATED AND FUEL FLOW CAN STOP. NHRA RUELS REQUIRE A VENT TUBE GOING THRU THE TRUNK FLOOR. YOU CAN TAKE A PIECE OF ALUMINUM OR COPPER TUBE ,BEND IT AROUND AN ENGIINE PULLEY 1 FULL TURN AND  THEN DOWN THRU THE FLOOR THIS CREATES A TRAP LIKE UNDER A SINK ,FUEL VAPORS THAT CAN CONDENSE ARE DRAWN BACK IN  ,PUT A GROMMET IN THE HOLE FOR A CLEAN LOOK .ON THE FUEL CELL END FLARE THE TUBE END (SINGLE FLARE IS FINE AND THEN BUY A VERY INEXPENSIVE #TUBE SLEEVE AND NUT TO SECURE THE LINE TO THE CELL FITTING .  GOOD LUCK KEITH ,JOHN