[Dagstar]

I'm in the midst of gathering parts to update to the LT4 fuel system(injectors, in-tank pump, HPFP) to support my incoming Whipple. From what I understand there's three lines to replace. My question is are there differences between the SS and ZL1 lines?

[ramairroughneck]

I would say get the hpfp feed line from a LT4 that doesn’t have the check valve and the duel 45 LT4 line just in front of the hpfp. I’m not aware of another but maybe somebody else can chime in for that third one and the difference that would make it beneficial.

[laynlo15]

There are two fuel pipes. Don't hesitate to buy them both and use them. They have a tendency to leak after one use. Some have done it with no problem, but for 75 bucks for both don't take a chance. King had his leak on the dyno after using the original ones off his LT1. I've purchased about 7 sets of those. Don't ask why as it should be pretty obvious with all the short blocks, blower changes and fuel changes.

[Dagstar]

Originally Posted by laynlo15

There are two fuel pipes. Don't hesitate to buy them both and use them. They have a tendency to leak after one use. Some have done it with no problem, but for 75 bucks for both don't take a chance. King had his leak on the dyno after using the original ones off his LT1. I've purchased about 7 sets of those. Don't ask why as it should be pretty obvious with all the short blocks, blower changes and fuel changes.

Yeah I read the posts by you, King, and others. I'm definitely replacing them. I was just wondering if there were differences between the SS and ZL1 lines. These are the part numbers I've come across on the forums:
12618337
12663577
12677005

[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

[laynlo15]

Nothing changes under the manifold, lines run in the same direction on the LT1/Lt4. Safety is number one, if you have a fire under the manifold because of a leak it will be too late to deal with it. Remember pressure at the fuel rail is 2900 psi at WOT, is it really worth not replacing them. **** no.

[Joshinator99]

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

Great info, thanks for sharing.

[laynlo15]

Everyone should have these numbers if your changing fuel pump, injectors or motor mods.

[Dagstar]

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

You rock, thanks for the info!

Originally Posted by laynlo15

Everyone should have these numbers if your changing fuel pump, injectors or motor mods.

Exactly. I was hoping I'd find a sticky or something with this information since so many go LT4 fueling.

[MSU120]

Originally Posted by Dagstar

You rock, thanks for the info!


Exactly. I was hoping I'd find a sticky or something with this information since so many go LT4 fueling.

Just so I’m clear....replacing all three is the way to go, right?

[Dagstar]

Originally Posted by MSU120

Just so I’m clear....replacing all three is the way to go, right?

As mentioned there's a possibility of a leak if reusing them, and I'm seeing about ~$140 for the price of all three pieces, so yes. My peace of mind is easily worth that.

[ramairroughneck]

Originally Posted by Joshinator99

Great info, thanks for sharing.

Originally Posted by Dagstar

You rock, thanks for the info!

Glad to help guys. Dagstar I’m forward looking forward to your Whipple build. Should be a lot of fun. Best Of luck with it

[L78toLT1]

Originally Posted by Dagstar

As mentioned there's a possibility of a leak if reusing them, and I'm seeing about ~$140 for the price of all three pieces, so yes. My peace of mind is easily worth that.

Agreed. Certainly worth it to prevent possible leaks. When I built my motor I was not aware that reusing these tubes could be problematic. I've got around 10K miles on the reused tubes so I suppose I got lucky. I will definitely change them the next time I have the motor apart.

[DorkMissile]

Depending on what you are working on (HPFP, Injectors, etc...) with some planning you can service the HP fuel system without removing the lines.

A year ago I went from LT1 to LT4 HPFP & Injectors, so I replaced the line between the HPFP and distribution block. So when I decided to tear down the engine this winter, I tool my time and pulled everything from the HPFP to injectors off together. Just took my time and didn't put too much pressure on anything as I took it off. Then set it down on a large piece of cardboard and blocked up the HPFP so there was no torque or twist on anything.

I had already upgraded to the LT4 intermediate line, so didn't want to take it apart. FYI - the feed line into the HPFP, you can take that on and off all you want, just make sure when you but it on you use a little lube to make it go on easy.

On the socket / ball connections on the lines, it can be done, but you have to understand how the seal works. The ball will make a indented ring where it meets the tapered face when the fittings are torqued. If separated, the ONLY way it will seal is if that indented ring is perfectly in the same spot it was when originally torqued. When re-assembling, you have to hand tighten the figging a little at a time, while slightly jiggling the line until you feel the two pieces start to align. When in the right spot, the fitting will tighten slightly farther than anywhere else. Then Re-tighten with 3 more Ft Lbs.

My best friend work as a dyno technician at the GM Proving grounds. Says they do it all the time to save time, but will occasionally get a leak (says it usually works once, but not to do it more than once).

Have to understand that the fuel pressure in these lines are so high (3000psi) that you dont have liquid fuel coming out, it comes out in a vapor. EXTREMELY combustable.