Author Topic: Fuel Line Question  (Read 20399 times)

Offline devildogmech

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Fuel Line Question
« on: May 28, 2025, 01:35:52 pm »
ok.... Truck is a 79' C-10 BIG Ten. In the midst of an LS Swap.

Fuel System.

- NEW Tank for an 87 C-10 with TBI
- NEW Sending Unit for TBI
- NEW Pump for LS

I'm trying to fabricate my fuel lines and weirdly, the connectors for the fuel injection system will NOT connect to the sending unit. The 3/8 Feed is WAY too small, the 5/16 Return is too big. The sending unit has the fuel injection style connectors........ Is there another size I don't know about?

Thanks in Advance.

Will
Be good, but not too good.

Offline VileZambonie

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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline devildogmech

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Re: Fuel Line Question
« Reply #2 on: May 31, 2025, 04:12:38 pm »
I'm using something very similar. It's like the pipe on the sending unit is the wrong size........ I'll go to AZ with my piece and see if I just got the wrong sending unit.
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Offline VileZambonie

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Re: Fuel Line Question
« Reply #3 on: June 01, 2025, 06:48:19 am »
Depending on what you have for tools you can make anything but if you are using the stock TBI pump, get this style adapter and use the AN fittings. You can buy everything you need from Evil Energy including lines, filters, fittings adapters etc. If you look on Amazon there are kits as well.

https://www.ievilenergy.com/products/an-male-to-sae-quick-disconnect-female

Here is an example of a Blazer TBI sending unit converted to push lock fittings.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline devildogmech

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Re: Fuel Line Question
« Reply #4 on: June 09, 2025, 11:11:15 am »
OK, I think I have it figured out. The 87' Sending unit has a "Butt Flare". This was the fuel fitting of the time. I checked and I think I have the correct fitting now. As soon as I know for sure, I'll let ya'll know.
Be good, but not too good.

Offline Captkaos

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Re: Fuel Line Question
« Reply #5 on: June 09, 2025, 03:12:58 pm »
you need 14mm/16mm O-ring to -6AN adapters to connect to the existing fuel and return lines on the truck I got mine from Pure Choice Performance.
5860 = 14mm
5870 = 16mm

You can get them just about anywhere though.

you can see them in use here: http://forum.73-87chevytrucks.com/smforum/index.php?topic=12120.msg208199#msg208199
This is where my whole LS swap was documented from start to finish
« Last Edit: June 09, 2025, 03:16:27 pm by Captkaos »