Fuel line loop - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tripmiester · 09-07-2020, 09:50 PM

Here is a pic of my tank it was a 6 cylinder I now am putting in a 454
Going to change the sending unit to a 3/8 line instead of the 5/16 that is in there now. My question is can I run the 3/8 from the sending to the fuel pump, to the Carb. Then run the 5/16 return line From the fuel pump to the Loop on the passenger side of the tank.

Thanks in advance for the advise!
Trip

Peanut74 · 09-09-2020, 09:20 AM

Don't see any reason it would not work. I assuming that you are using the factory fuel pump and a normally aspirated carb based on your post.

3/8" line has 0.11 sq-in and 5/16" line has 0.07 sq-in for a difference of 0.04 sq-in. Feeding that big block should easily make up for the difference.

Andy4639 · 09-09-2020, 10:32 AM

I'd take the roof cab loop out and just rubber hose the two lines together. That way if there is a leak it's only right there. Not really sure why you want a return line though tobegin with unless your going to run a electric pump. No need for a return on a mechanical pump.

Tripmiester · 09-11-2020, 08:39 AM

Well that is my question, did not know if i needed the loop and a return line, so if I cap the tank where the loop returns to, and just have a mechanic fuel pump I can just run the feed from the 3/8” sending unit and a 3/8 hard line through the floor and to the pump no return line cap the extra hole in the floor and be done. Correct?

Andy4639 · 09-11-2020, 10:03 AM

Quote:

Originally Posted by Tripmiester

Well that is my question, did not know if i needed the loop and a return line, so if I cap the tank where the loop returns to, and just have a mechanic fuel pump I can just run the feed from the 3/8” sending unit and a 3/8 hard line through the floor and to the pump no return line cap the extra hole in the floor and be done. Correct?

Yes but I would leave the loop it is also for expansion of the gas if you over fill it.

Tripmiester · 09-11-2020, 11:43 AM

So if I get a mechanical pump with a return line I have the 5/16 return line in the frame already and the loop is thru the floor already, like I mentioned before I could have the 3/8 sending unit send fuel to the pump with the 3/8 then connect the 5/16 return back to the loop. Otherwise I’ll have to cap one side of the loop off. Thoughts?

Andy4639 · 09-11-2020, 04:42 PM

The loop is for the charcoal canister up front under the battery if it's still there. I would just cap it off and forget about it unless you have to have the truck inspected.

Tripmiester · 09-11-2020, 08:12 PM

Thanks for all the info!
Have a great weekend ��

09-07-2020, 09:50 PM	#1
Tripmiester Registered User Join Date: Jul 2018 Location: Bethany Connecticut Posts: 360	Fuel line loop Here is a pic of my tank it was a 6 cylinder I now am putting in a 454 Going to change the sending unit to a 3/8 line instead of the 5/16 that is in there now. My question is can I run the 3/8 from the sending to the fuel pump, to the Carb. Then run the 5/16 return line From the fuel pump to the Loop on the passenger side of the tank. Thanks in advance for the advise! Trip Attached Images

09-09-2020, 09:20 AM	#2
Peanut74 Registered User Join Date: May 2018 Location: Prattville, AL Posts: 590	Re: Fuel line loop Don't see any reason it would not work. I assuming that you are using the factory fuel pump and a normally aspirated carb based on your post. 3/8" line has 0.11 sq-in and 5/16" line has 0.07 sq-in for a difference of 0.04 sq-in. Feeding that big block should easily make up for the difference. __________________ -------------------------------------------------------- 1967 C10 "Snowball" (Currently in a million pieces down from a bazillion) 1989 Toyota DLX pickup "The Hulk" 2012 Jeep JKU "Crush" 1976 Chevy short bed with a 327 and 3 on the tree (Sold it to buy the Blazer) 1971 Chevy Blazer (Sold it)

09-09-2020, 10:32 AM	#3
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Fuel line loop I'd take the roof cab loop out and just rubber hose the two lines together. That way if there is a leak it's only right there. Not really sure why you want a return line though tobegin with unless your going to run a electric pump. No need for a return on a mechanical pump. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

09-11-2020, 08:39 AM	#4
Tripmiester Registered User Join Date: Jul 2018 Location: Bethany Connecticut Posts: 360	Re: Fuel line loop Well that is my question, did not know if i needed the loop and a return line, so if I cap the tank where the loop returns to, and just have a mechanic fuel pump I can just run the feed from the 3/8” sending unit and a 3/8 hard line through the floor and to the pump no return line cap the extra hole in the floor and be done. Correct?

09-11-2020, 11:43 AM	#6
Tripmiester Registered User Join Date: Jul 2018 Location: Bethany Connecticut Posts: 360	Re: Fuel line loop So if I get a mechanical pump with a return line I have the 5/16 return line in the frame already and the loop is thru the floor already, like I mentioned before I could have the 3/8 sending unit send fuel to the pump with the 3/8 then connect the 5/16 return back to the loop. Otherwise I’ll have to cap one side of the loop off. Thoughts?

09-11-2020, 04:42 PM	#7
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Fuel line loop The loop is for the charcoal canister up front under the battery if it's still there. I would just cap it off and forget about it unless you have to have the truck inspected. Attached Images __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

09-11-2020, 08:12 PM	#8
Tripmiester Registered User Join Date: Jul 2018 Location: Bethany Connecticut Posts: 360	Re: Fuel line loop Thanks for all the info! Have a great weekend ��



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