Fuel rail mod

[moparzrule]

Just wanted to do a little write up of modding a stock rail for more than 350 WHP without having fuel starvation. How much more HP this is capable of I don't know, but IMO it increases flow a ton over stock.
OK. I did this to a 1 piece rail, simply because I didn't want to hack up a 2 piece for an experiment LOL. But it should be the same for a 2 piece rail as far as I can tell.
First I drilled a hole at the fuel inlet side on the main body of the rail(refer to pics), started with a small bit like 1/4'' and progressed up to 15/32'' because I wanted to tap this 1/4'' NPT for a fitting. This part is about 1/2'' thick but go past that part and drill into the inner tube another inch or so.
Next, you have to remove the dampner off the end. It's a little tricky because you can't fit a wrench on the outside ''nut'' of the dampner. So basically I used a cutoff wheel and cut off the dampner leaving the rest of the nut to thread it off. Sorry but I forgot to get a pic what that looks like. After you get it off, you'll see the inner tube. I just took a drill but, started out with a like a 5/16'' and worked my way up to 15/32'' again. After you drill this side out, the inner tube will eventually break free and be able to come out. It may take some persuasion, be patient and resist smashing the rail against the wall. I used a screwdriver, but be careful not to mangle it up too much in there as it won't fit out the end then.
Now, tap both ends for 1/4'' NPT. If you have the tap, the stock inlet is perfect for the 7mm. This is just as a precaution, the 1/4'' NPT fitting going into the main body should go past the stock inlet (refer to pic). 7mm bolts are hard to find, but I found one at Lowes, seems about 20mm long is about perfect.
Next you need to go get fittings. I thought the threaded Dampner end was 3/8'' NPT, but the fitting just won't go on. This is the other reason I went ahead and tapped 1/4'' NPT on the inside, I need to make another trip to the store. Another option is to just buy a 1/4'' pipe plug, as it's not really needed but I am going with a dual fuel inlet feed to make sure that number 4 injector does not starve for fuel.
With the dual feed inlet, I have no reason to doubt that this should support 450+ WHP. The body inside is nearly double without the inner rail.
Thats about it, I'll let the pics do the talking now.

[moparzrule]

Just an update it appears the thread on the dampner end is 5/8'' 18 TPI, which is 1/32'' larger than 3/8'' pipe thread, and 3/8'' pipe thread is 18 TPI. No wonder it looked so close. This is why the 3/8'' NPT 90* elbow will not thread onto it, but it's so close I'm pondering if I run a 3/8'' NPT die down it if it will work. Ahh, I'll probably end up just getting a 1/4'' NPT 90* fittings and use the inside where I tapped.
Oh, and just remember to use some kind of thread sealer that is gas resistant or you can always solder or braze it. I'll probably solder it.

[moparzrule]

I may offer this as a service, anybody interested?

[BadAssPerformance]

...It may take some persuasion, be patient and resist smashing the rail against the wall....

LOL, It doens't look easy to get out.

I have one another guy made, but IIR he welded kuston fittings on the ends so that he didnt have to figure out what thread it is.

[turbovanman²]

Sometimes they tack weld the little tube halfway down. One fuel rail I did it just slid out, another one I had to cut the fuel rail in half and cut/grind the spot weld,

[moparzrule]

Sometimes they tack weld the little tube halfway down. One fuel rail I did it just slid out, another one I had to cut the fuel rail in half and cut/grind the spot weld,

I just found this out myself. I started to mod a 2 piece rail, after drilling both ends the inner tube is free on both ends but it's tacked in the middle.
I'm gonna try to hammer a screw driver through there and break the tack weld.
More pics to come.

[moparzrule]

Pic of dampner end just after removal-

Used a 3/8'' drill bit first-

Then the 15/32'' bit to finish it off ready to be tapped-


I drilled down in with the 15/32'' bit about an inch and a half or so, to make sure the ends of the inner rail are free.

[moparzrule]

Where there's a will there's a way. Finally got that tacked on inner tube out, shove an extra long screw driver down where the tack was, beat on the end with a hammer and it broke the weld no problem.


This fuel rail already had the inlet broken off, so I just tapped it where it was and put the 7mm bolt in. Thats a 20mm bolt and it's all the way up against the brass fitting. I had a 16mm bolt in there but it didn't really leave much threads to see to solder that shut.
Next step solder, then finished!

[moparzrule]

Anybody have any thoughts as to not running the dampner? I mean, the aftermarket rails don't have them so I know it will work OK, but just curious.

[gvare001]

I think it should be OK, my FWD fuel rail doesn't have one. SRT-4's fuel rail don't have one either.

[gvare001]

Oopps, SRT-4's fuel rails do have a dampner, but as you said aftermarket ones do not.

[turbovanman²]

Dodge did it to help soften the pulses of the fuel pump, newer pumps don't have that issue.

[moparzrule]

Is it really an issue that needs attention? I have a walbro 255 pump, which would be the same model for 91+ anyway since it's like universal.

[turbovanman²]

Is it really an issue that needs attention? I have a walbro 255 pump, which would be the same model for 91+ anyway since it's like universal.

Nope, don't worry about it. Old pumps had issues, GM used dampeners too but you throw them away when you change the pump. Technology rocks,

[moparzrule]

Yeah I suppose that TU and FWD-P figure if you are running one of their rails you are probably making atleast over 300 WHP so you are gonna have an aftermarket pump.

[badandy]

The aftermarket rails also have enough volume where pulses are not a problem therefore there was no need for the damper.

[moparzrule]

Well with the inner tube out it almost doubled the inside size, so it will probably be OK.

[iTurbo]

Just an FYI, my Spirit R/T didn't come from the factory with a damper on the rail or in the fuel pump module. Also when installing a Walbro pump in my SL, I had to remove the damper at the pump because it used a banjo fitting and was not compatible with the Walbro. Never had a problem with it.

[badandy]

Just an FYI, my Spirit R/T didn't come from the factory with a damper on the rail or in the fuel pump module. Also when installing a Walbro pump in my SL, I had to remove the damper at the pump because it used a banjo fitting and was not compatible with the Walbro. Never had a problem with it.

Well there is another reason for that. Your R/T was not batch fire like the earlier TD/SD models...it is sequential...so only one injector is open at a time. Batch fire has two injectors firing at a time. Due to this and the volume of the factory fuel rail it is more difficult to keep the pressure constant...hence the need for the damper to absorb the pulses. If the fuel rail has enough volume it will naturally dampen itself. This is why aftermarket rails do not need a damper.

[badandy]

Well with the inner tube out it almost doubled the inside size, so it will probably be OK.

I think you will be okay just as long as you don't have to run low fuel pressures.