New twist on the dual fuel feed mod?

[elkhtr]

So, I was wondering if anyone has attempted the dual feed mod using the crossover tubes as a feed point instead of the plugs in the ends of the cylinder heads.
I would think that if dual feed from the ends is an improvement, wouldn't dual feed from the centers be even better.
This way at least I wouldn't have to cut a hole in the firewall.
I am thinking of machining some small blocks with the appropriate features to replace the crossovers and create an accsess point for fuel lines.
Is there any reason people are using 3/8 tubing for this mod, when the minute it gets to the head it is restricted down to 1/8 pipe?
I was thinking of using 1/4" tube to match the size of the crossovers I would be removing.
Also, if anyone has one of these crossover tube assemblies for sale I would be interested.
I don't want to disable my truck while I reverse engineer the replacements.
Can't wait to hear some feedback on this idea.

 

[Jeepsinker]

Huh? Please elaborate for those who don't live with you?

 

[patracy]

I have thought about this path as well. But I doubt you'd see much more of an improvement for the effort than the dual feed. The dual feed addresses the "leftovers" that #5 and #6 sees supply wise. With the dual feed, only #2 and #3 are getting the shortest supply. But they have fuel from each end and could overlap each other with fuel from the rail. 2 and 3 do not fire back to back.

 

[elkhtr]

Jeepsinker, sorry, I assumed too much.
this is dealing with the single line fuel delivery to the front cylinder head on the nhc 250.
the "standard mod" removes a plug in the rear cylinder head, and ads a second fuel feed line from a tee at the pump.
Search dual fuel line, and you will find the other threads with photos.

Patracy, I was hoping you would weigh in on this.
after thinking about this a bit more I am going to try it at the crossovers just because it seems easier then removing the shift tower, etc, and cutting holes in the firewall.
I think i will try piercing the crossover tube and silver soldering a fitting to the tube.
Some extra support brackets for the tube and it should be a durable setup.
Having done this mod to your truck, are you still happy with the results?

 

[patracy]

I can't advise your idea honestly. There's too much pressure/vibration/stress to trust a solder job. If you really want to go down that path, I'd take the crossover tube out completely and have flare fittings TIG welded onto them to allow you to plumb it up.

When it comes to the shifter, it's only 4 bolts that hold it to the doghouse. The doghouse can also be removed from the cab to access the engine better.

I'm very happy with the results.

 

[elkhtr]

Thank you for the input.
The type of silver solder I was considering is very strong.
We use it to make extended drill bits, butt solder 1/2" drill rod to a 1/2" bit.
Routinely push that through 4" of steel, never had one fail at the joint.
That said, tig welding is an option for me also, and I might go that way.
Maybe even tig weld with a coat of silver over the top just to remove any chance of pin holes.
The stress and vibration issue is very much on my mind.
Whichever rout I take I will bracket the setup to mitigate this.
Thanks again for your feedback!

 

[VPed]

Flex line would relieve strain but yeah, I would not think of cutting a hole in the firewall over unbolting the doghouse.

 

[elkhtr]

My mistake on the firewall cutting issue.
I believe that is an 800 series issue.
Should have looked closer before including that comment.

 

[162tcat]

I think this is being over engineered. The dual line feeds 400hp+ engines just fine. Ours are only 240hp and could possibly be pushed very carefully to 350hp but 300hp is more realistic. I'd be willing to bet that absolutely no gain would be noticed over the standard dual fuel mod, even on a dyno. No reason to reinvent the wheel. But I do like your thinking outside the box!

 

[patracy]

I think this is being over engineered. The dual line feeds 400hp+ engines just fine. Ours are only 240hp and could possibly be pushed very carefully to 350hp but 300hp is more realistic. I'd be willing to bet that absolutely no gain would be noticed over the standard dual fuel mod, even on a dyno. No reason to reinvent the wheel. But I do like your thinking outside the box!

I would agree with that. However, doing the dual fuel line with "bolt on" hardware is certainly worth it and noticeable in performance.

 

[162tcat]

Agreed. I did the dual fuel on mine, idles smoother now and is more responsive. I didn't notice a power gain though.

 

[patracy]

Agreed. I did the dual fuel on mine, idles smoother now and is more responsive. I didn't notice a power gain though.

I do not believe I gained any "more" power from it. However as you pointed out, response has certainly improved. And I swear I feel better midrange. Which this is what I'd expect honestly. The engine is still going to be limited by the PT output same as before. But the dual feed will help idle/response and possibly beef up areas from idle to governed fast idle.

 

[elkhtr]

Well I decided to do it the way you folks did.
Got the shifter and doghouse removed, found the plug and proceded to turn my proto 3/16 allen bit into rotini.
About the time I thought it was going to break, the setscrew jumped a flat and that little impact broke it free.
Weather permitting the install starts tomorrow.
162tcat, where in Washington are you?