Duramax fuel line replacement

B

Blackmax123

Member
Aug 2, 2014
683
1
18
central Pennsylvania
I'm looking to replace all my restrictive factory hard fuel lines with 5/8 an line. I know I've seen a few treads on this before and I have some good screen shots I took. But up at the engine I want to put a junction block to run my feed lines into then out to the cp3's. Also want to run a junction block to tie all the returns into. The what is everyone using for this??

I've done some searching but can't seem to find the good tread. I read that had some information on what guys are really using.

Here's a picture of what I'm trying to accomplish. And a picture on the one block I've found only issue is it is 1/4npt but I thought I could probably drill it larger and retap the ports.
 

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K

Kunz111

Member
Jan 16, 2016
113
2
18
Bumping this back up as I'm putting a s369sxe and 10mm stroker on my truck right now and I just saw how much of a cluster mess the stock fuel line stuff is, I would like to switch everything up also. I have been doing a lot of reading but I'm still really confused about things and I was wondering if someone could help me understand this better.

As I look right now at the stock stuff The big feed line comes into the engine bay goes across the top of the cp3 to where the stock fuel filter house would be but sense mine is deleted it's a hose that connects back to a hard line where the pressure test port is, splits to a T , the hard lines go to the back side of the ybridge, and one goes to a rubber hose and then the cp3 and the other goes back to the driver side head area and Ts off again where one goes to another rubber hose and then the cp3, and the other one goes towards the firewall where it has a fuel temp sensor the return line to the tank and another rubber hose going to the driver side fuel rail.

So all of that would get pulled out and then would I run a 8 an up to the cp3? Then get a block and run the return from the cp3, fuel rail, and the injectors too? Also put the fuel temp sensor in. Am I kinda close or am I way off here?
 
ikeG

ikeG

Oughta Know Better
Apr 19, 2011
2,464
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Western PA
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Kunz111 said:
Bumping this back up as I'm putting a s369sxe and 10mm stroker on my truck right now and I just saw how much of a cluster mess the stock fuel line stuff is, I would like to switch everything up also. I have been doing a lot of reading but I'm still really confused about things and I was wondering if someone could help me understand this better.

As I look right now at the stock stuff The big feed line comes into the engine bay goes across the top of the cp3 to where the stock fuel filter house would be but sense mine is deleted it's a hose that connects back to a hard line where the pressure test port is, splits to a T , the hard lines go to the back side of the ybridge, and one goes to a rubber hose and then the cp3 and the other goes back to the driver side head area and Ts off again where one goes to another rubber hose and then the cp3, and the other one goes towards the firewall where it has a fuel temp sensor the return line to the tank and another rubber hose going to the driver side fuel rail.

So all of that would get pulled out and then would I run a 8 an up to the cp3? Then get a block and run the return from the cp3, fuel rail, and the injectors too? Also put the fuel temp sensor in. Am I kinda close or am I way off here?
Click to expand...
Sounds like you get the drift!

Sent from my XT1585 using Tapatalk
 
B

Blackmax123

Member
Aug 2, 2014
683
1
18
central Pennsylvania
Hopefully I'll put the finishing touches on mine tonight. I left the fuel temp sensor where it is. I cut the fuel return tune off the junction block where the fuel temp sensor is and threaded it. Then installed a pipe plug to block it off. I then cut the hard line and got a compressor fitting from Carl's that goes from hard line to -6 An.

I got block from mcmastercarr and made a mount to place them right beside the two big engine harness bale connectors.
 
K

Kunz111

Member
Jan 16, 2016
113
2
18
Awesome now I have a couple of more questions. How does everyone get the injector return lines connected to the fuel block? Those lines are very small. Also for the cp3 do I have the feed and return ports pointed out right?

 
Wikid

Wikid

Machinist and Know things
Oct 21, 2016
88
0
6
Texas
When I did my return block I found that the -3an fittings for brake lines fit well on the injector returns so I used that to get them to my return block. Haven't had them leak at all.

As for a return block I made my own.
 
K

Kunz111

Member
Jan 16, 2016
113
2
18
Thanks for the correction 04jimc.



Wikid said:
When I did my return block I found that the -3an fittings for brake lines fit well on the injector returns so I used that to get them to my return block. Haven't had them leak at all.

As for a return block I made my own.
Click to expand...

So did you just slide the hose over a threaded fitting and clamp it down?
 
Wikid

Wikid

Machinist and Know things
Oct 21, 2016
88
0
6
Texas
The fittings I have looks very similar to larger AN fittings, you have to trim back the braiding as its molded in with the rubber hose.

It has the nut you slide over the hose, then you slip the any fitting into the hose and run the nut up and as you tighten the nut it will clamp down on the hose.

Check out my build on Instagram you'll see the return block a few down and see the AN fitting attached to the hose. I do plan on redoing this block to be better flowing.

https://www.instagram.com/w1kid/
 
Wikid

Wikid

Machinist and Know things
Oct 21, 2016
88
0
6
Texas
TheBac said:
Pretty nice idea.

http://www.instagram.com/p/BSEn9F9DS3e/?taken-by=w1kid
Click to expand...

yea that!, sorry terrible at linking specific photos.

Since i have the race valve I prob didn't need that return line but I figure the fitting is still on the rail so I plumbed it. It still has the fuel return temp sender also.

I did a -6 return thought about making it a -8 since the bigger pump but haven't had any issues that are related to lack of fuel return volume.
 
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