[qnitro]

The S Pipe is definitely different.. The LT1 S Pipe tilts upward and is OK if mounting a LT4 on a LT1 because of adapters, but the LT4 sits lower and you need a LT4 S Pipe, GM 12677003.. ask me how I know

Originally Posted by ramairroughneck

12677005 dual 45 bend LT4 high pressure fuel line

12618337 Is another version of one listed above. It has one 90 and one 45. It comes on LT1, L83, L86. If you use the one above you won’t need this one

12663577 is LT4 hpfp feed that doesn’t have the orifice check valve like the original SS LT1

12677002 S shaped line between rails. I believe it’s used on all engines. If you’re just wanting to change all lines to eliminate the chance of a leak

[EDFHOBBIES]

I would use the LPE ck valve I picked up more than 5 psi of low side under load that was with the stock pump and DSX aux. feeding the high side really helps!

[Joshinator99]

Originally Posted by EDFHOBBIES

I would use the LPE ck valve I picked up more than 5 psi of low side under load that was with the stock pump and DSX aux. feeding the high side really helps!

Agreed, running the LPE check as well. The OEM check valve is insanely small.

[Puddin]

So are we supposed to use 12677003 or 12677002 when replacing the s shaped line?

[Joshinator99]

Originally Posted by Puddin

So are we supposed to use 12677003 or 12677002 when replacing the s shaped line?

002 is the one I use FWIW

[Puddin]

Originally Posted by Joshinator99

002 is the one I use FWIW

Cool that's the one I purchased but just wanted to make sure In case I have to return it for the other one. Appreciate the help Josh.

[Joshinator99]

Originally Posted by Puddin

Cool that's the one I purchased but just wanted to make sure In case I have to return it for the other one. Appreciate the help Josh.

No problem! I saved this post from a while back which was really helpful and have to refer back to it since my car gets taken apart pretty much every spring... lol

[christianchevell]

https://static.nhtsa.gov/odi/tsbs/20...32139-0001.pdf

I am using the 12677003 for a lt4 but have not verified until tear down for the Magnuson 2650, the numbers are in this Bulletin for the Lifters and describes using the same number on the pipe existing and says there is a difference...? But they look identical.. but the 002 says lt1 and that theres two designs for each.... The numbers are really small on the tags attached to the lines...