Hot Rods Sbc fuel pump with 3 connections ?

I have a sbc 305 and the fuel pump has 3 connections I've never seen this before what is the third connection for? Can I cap it?

 

Someone mentioned fuel tank vent, it is part of the clean air stuff and not at all necessary for the operation of your car.

 

The extra line usually goes to a canister to collect vapors. Emission stuff.

 

The third line is return line back to tank.It was to help cure vapor locking . I have block them off

 

Its the smaller line

 

The third line is not a vent, it's the return line to the tank. Helps with vapor lock issues, if you can run the line to the tank, then do it. Or get a two fitting pump instead, if you don't want the return line. They only cost $20. and you didn't want to put an old used pump on your car anyways.

 

Yes it is a return. Some years ago when we had a fuel shortage, I had a van and I installed a second fuel tank with a three way valve. Only the stock tank had a gauge, so when I ran on the second tank, the fuel gauge would actually rise when I drove because of the return.