425 Olds fuel pump question

I got a mechanical fuel pump for my 1965 425 Olds from a Starfire laying around, but it's got 3 connections. One is for a threaded fitting, and two for fuel hoses. The two for the hoses are different sizes.
So I was told that the smaller one is for a return line to the tank.
Is that right and do I have to use it, or can I just plug it up?

I can post some pics tomorrow, but maybe somebody knows what I'm talking about and can help me right away...

Thanks, Martin

 

You are correct, the smaller hose fitting is simply the return line to the tank and you can cap it if you don't have a return line on the car. The threaded fitting goes to the carb and the larger hose fitting is suction from the tank.

It is a good idea to run the return line if you can since this helps prevent vapor lock by circulating hot fuel back to the tank to cool off. Olds used the return line on all cars that potentially had high underhood temps, mainly A/C cars and high perf cars. With the ethanol in fuel today, vapor lock on carbureted cars is even more of a problem.

 

Thanks, Joe!
So my vented gas cap should help prevent vapor lock though, right?
One of the problem is, that the gas tank I am using doesn't have a connection for a fuel return.

 

I have heard of people running the return line into the filler neck. That may be a easier way to add the return.

 

You can also run the return back into the feed just before the pump with a T.

I did that for years until I got a fuel pump with only 1 outlet

You can see my old fuel pump here with the T installed

http://59chevypickup.webs.com/apps/photos/photo?photoid=80193203

 

I just capped it on my 455 Olds and haven't had any issues with it in my 55 Caddy