Putting my engine back together and I originally was going to use 60lb injectors for my combo. I rebuilt my engine so I should be able to make more power with major boost. If I go with about a ~80lb injector are the stock rails even capable of handling that much fuel or do I need to go custom fab?

 

I'd go with new rails and minimum of -8AN feed line, -6AN return and an Aeromotive regulator and external pump (or dual walbro pumps in tank)..

 

I am in the process of building a procharged 383 and have come across this same question with not alot of info available on thirdgen org. Mostly because alot of guys go for the carb rout and then charge it. I went with 8AN feed line, -6AN return lines and a dual intank pump by ww.lonniesperformance.com/ he is currently putting a system together for mine the first dual intank he has done on thirdgens. Give him a call and talk to him. camaroz28.com has aton of guys that have gone this route. I haven't come with a solution on what I am going to do at the rails but am working on it. I can keep you informed of my route if you would like. I am hoping to get the motor in and stuff with in the next month. Hope this helps a little.

 

I discovered something very interesting about the stock fuel rails. If you cut off the hard inlet tube and drill out the remains of its fitting, what comes in view is a restrictor built into the fuel rail. I didn't take the time to measure the opening but it was surprisingly small. Before I had a pair of -06AN fittings welded to the front of each rail, I had this restrictor drilled out. It's definitely the bottleneck. Once it's drilled out, I cannot see any other restriction that would impede flow to any of the injectors.

 

that's good info there Willie. I had no idea the rails were crippled like that.

 

Me neither. I was shocked!! I'd guestimate the diameter of this hole where ALL the fuel must navigate through prior to branch off to the driver's side was on the order of <1/8-inch.

Willie

 

I found some aftermarket TPI stuff from searching the internet but I don't know if it's still available.

http://go.mrgasket.com/pdf/4311M.pdf

http://performance.drivewire.com/get...|Fuel%20System

I wonder if you used 6AN into each fuel rail would that be adequate for 800-1000hp so long your fuel line was sized right?

Fuel line size is determined by the horsepower of the engine.
Up to 350 HP 5/16" or 4AN
Up to 500 HP 3/8" or 6AN
Up to 700 HP 1/2" or 8AN
Up to 1200 HP 5/8" or 10AN

 

Personally, if I were building a high HP car like that, I would have a -10 from the tank to a y-block with 2 -8's going from the y to the rails and 2 -8's from the rails to a regulator with -8 going back to the tank.

 

my planned setup is an aeromotive a1000(have it already), an aeromotive bypass reg.(boost), and aeromotive inline filter and a -10an braided stainless feed line. I'll be using the original 3/8 line as the return thus ditching the smaller original return line that came on my car......

I like the idea of the y, but I believe aeromotive makes a reg. with 1 feed with 4 extra ports.cap one or use it as the source for a gauge. use one for each rail and the last to return......

May still have to use another y to properly regulate the pressure though

HTH!

 

If the stock fuel rails are anything like the stock LT1 fuel rails they’re probably bigger then most aftermarket rails inside once you get rid of the factory fittings, and they shouldn’t be and issue at that point. I could go and measure a set that I have disassembled, but from memory I would guess that the internal passage is somewhere in the range of 5/8-3/4” and almost round with a flat bottom. The TPI rails are externally similar but slightly smaller, but that would still make them huge.

As far as some of these almost obscene line sizes… the stock 3/8” hard line (about the same as a -6 braded) with dual intank 255L/hr pumps will feed something in the range of 1300hp… I really don’t see why anyone here needs to go with -8 or more so -10 lines unless they’re planning on trying to feed that kind of volume to a carburetor at low pressures…

 

I have a set of factory rails modified with -8 inlets and -6 outlets. I am not using them, so if anyone is interested, I will ship them anywhere in the us for $50.

DonB.

P.S. I ran these in a 3500lb Firebird and went 10.80's at over 130mph, that puts it at over 800hp. I will say that the stock rails have the same ID as the MSD fuel rails which I use (i am making over 1400hp).

 

SO can you just hog out the rails and tap it for AN fittings then ? Or is it a must to have them welded in ?

 

see a couple replies down for some pics I took while doing modifications to my fuel rails. ( the pic was huge when I attached it)The view you are seeing is the front of the passenger side rail, where the fuel inlet is. I drilled, tapped, and plugged the factory inlet. I am using the cold stat opening in the back of the driver's side rail for my fuel inlet now. I did this so my fuel lines would not run accross the front of the motor. The dimensions were done with a micrometer so they are pretty accurate and not just guesses.

 

What pics?
----------
I see now... I imagine welding in AN fittings would be better.

 

https://www.thirdgen.org/forums/tpi/...fuel-rail.html

I broke my finger and have yet to make any more progress on what you see in that thread, but smaller pictures can be seen

 

just curious how much would the stock fuel rails allow for in hp? thanks guys

 

Any idea how much power the stock rails and fuel lines can support w/out being modified? If you have a big enough pump/pumps when do the stock fuel rails and fuel lines become a restriction?

 

My car has the stock rails and lines all the way to the tank. With just a walbro intank, im making close to 600rwhp. But they might be close to maxed out.

 

TurboedTPI-thanks for the response, that makes me feel a little better. What walbro pump are you running?