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Discussion Starter · #1 ·
Do I need a fuel return line on my car? It is a 70 SS BB car. If I do what it a steel line or rubber? Just for verification what size fuel line is on a BB car?
 

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HAd this question myself. I run 3/8 on my BBC, but the return (I think) was 1/4, could be wrong. I have the return on my pump blocked off and the return hose is capped. But I have the same question as you, should I be running it? What are the downsides to capping off the return? And then, how to deal with back pressure in the tank, vented caps = leaks.

Anyone? I know this has been covered moderatley in the past, but no search feature...also dont remember seeing a fix.
 

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I don't know what the risks are if you don't run the return line, but I know some people do it. The factory steel return line on my 70 396 (402) is 1/4". The steel fuel line is 3/8". Both have short rubber hoses to cennect them to the tank & fuel pump.
 

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If you have a problem with back presure in your gas tank when you remove the cap at the gas station like i did you will benefit from using a return line.I had this problem and bought a new correct fuel pump the long style with the return and hooked it all up and it fixed that problem.This was on a 70 ss 396 also.

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My 70 Chevelle SS & 56 Pro Street Chevy
 

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I have seen much discussion on this topic and I can share my personal experience on this one. This is all AFTER rebuilding a motor twice because it smoked and we thought it was a bad ring seal from the first rebuild.

After much investigation/frustration it turned out to be the return line PLUGGED.
When this happened the fuel pressure would be a steady 6-7 lbs at idle. However when you ran the car up to 5K+ RPM the fuel pressure would climb to 12+lbs. and overcome the needle and seat on the Holley and flood the engine to the point of washing down the rings.

After digging in to this for a LONG WHILE we found that the fuel return line served 2 primary purposes;
-move fuel to prevent vapour lock and
-help to regulate fuel pressure.

After all of the hassles I had, I run both the supply and return line and check the return regularly as the blockage was from a small piece of rubber from within that little piece of rubber hose between the pump and the return.

If you run a pump that was made WITHOUT the return you would/should be allright as well.

By the way, I thought ALL BB cars except LS6 cars had return lines. Also, don't all small block cars also have fuel return lines ??

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Team Chevelle # 279
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Discussion Starter · #6 ·
So does the return line run right along the feed line? If so, by the looks of my frame, there was never two lines next to one another. So what does this mean? If I do need to run another line, does it have to be metal or a rubber line? Thanks.
 

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LevonH Thanks for that post. When I take my gas cap off, there is a real rushing of air. I have also noticed a small amount of smoking, but not useing any amount of oil to speak of.(Sure us a pile of gas though!) I think you may have just solved my problem as well. Man this site has saved me a lot of hard earned coin, not to mention time since I joined. You folks with no flag beside your name, I encourage you to sign up and join. Some of the best money I have ever spent!
 

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1BAD402, yes ..the return runs parallel to the feed line and could have been removed by a previous owner, or cut and capped, not visible in the engine bay.

LevonH, thanks for the input, that pretty much clears it up for me. Didnt know it regulated pressure as well. Looks like im cuttin and splicin' this weekend and hookin that sucker up. Thanks.

1BAD402, when I hook mine up , i'll let you know what happens.

Beaux

[This message has been edited by Midnight Marauder (edited 09-24-2001).]
 
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