Ok so I was thinking the other day...
What exactly is the second (smaller) fuel line that goes to the mechanical fuel pump? I know that the big one carries fuel to the pump, so does the other one return it to the tank? I was wondering becuase my 327 has a fuel pump with only one inlet for the fuel and I plugged the other smaller hose. Whenever I take the cap off the gas tank there is a vaccum and air rushes in, wouldent this vaccum cause fuel satrvation? I'm thinking of modifying my gas cap so it will vent and then there wont be any vaccum. Would this be wise or not? Oh, and I dont have to worry about emmisions here.

Thanks,
Andrew

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1983 Firebird
327 bored .030
4-speed manual
Edelbrock 600cfm carb.
Edelbrock Performer intake / cam.
Pete Jackson gear drive.
MSD 6a ignition
yackety, smackety, blah, blah.

 

It was indeed a return line. However, that shouldn't be causing your vacuum/pressure problem at the gas cap. That's the function of the charcoal canister. If you removed that and plugged that line, then there's your problem.

The canister doesn't cause any performance penalty other than its weight, which is small. It's a nice way to provide a filtered vent to the tank. If you've removed it, consider replacing it. If you didn't remove/plug it, you need to service it (replace filter, check for plugged lines, non-functioning valves, etc.). Now that I think about it, you may have simply disabled it with your carb replacement, and just need to provide vacuum to the valve(s) on the top of the canister.

The return line isn't a bad idea for the fuel pump, either. It can help prevent over-pressurization of the carb and flooding. It will also keep the fuel to the pump cooler in low demand situations. I'd suggest getting a good pump with the return line and running it. Or, get a 3-port regulator to do the same.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, TBD heads, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Thnak you for the info five7kid, I really apreciate it. Finally I have comfermed what that hose was.

Andrew