Replacing fuel line with 3/8 - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 10 (permalink) Old 05-11-2019, 05:14 AM Thread Starter
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Replacing fuel line with 3/8

My 64 Galaxie has 5/16 fuel line. I want to install 3/8, but the pre bent line I see inline is for big blocks, and appears to go to the passenger side to fuel pump.
Of course, the small block's is on driver's side.
What is the best approach to replacing the line? Someone mentioned using steel or aluminum 3/8 brake line (cheaper) and bending it myself.

1964 Galaxie 500 351C 4 speed
1971 Pontiac Trans Am 455 HO
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post #2 of 10 (permalink) Old 05-11-2019, 08:09 AM
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My 69's fuel line (original 3/8") runs from the tank up to just behind the bottom rear of the front fender then rubber from there up to the carb. The rubber part may not be original I dunno about that but you could buy the prebent 3/8" line then rubber or stainless etc to get to the carb.
I'm no mechanic so maybe there's a better way but it works for me.
Scott.
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post #3 of 10 (permalink) Old 05-11-2019, 03:41 PM
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Re: Replacing fuel line with 3/8

I think your small block is going to have large enough fuel need to justify a 1/2" fuel line.

Iowan
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post #4 of 10 (permalink) Old 05-11-2019, 06:07 PM
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Re: Replacing fuel line with 3/8

All the mechanical fuel pumps on Ford V8s are on the driver's side.
DeepRoots and Ddepascal like this.

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1970 Galaxie 500 Sportsroof.
1963 1/2 Galaxie 500 Fastback.
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post #5 of 10 (permalink) Old 05-11-2019, 06:24 PM
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Re: Replacing fuel line with 3/8

I use -8 braided hose. Couldn't be easier to run, and much easier to isolate from heat.

1976 F100 390/c6
1963.5 Galaxie 446FE/c6
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post #6 of 10 (permalink) Old 05-12-2019, 05:45 AM Thread Starter
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Re: Replacing fuel line with 3/8

That briaded hose sound like a good idea. Only about $110 for 20 ft. of #8. Are there fittings for it to attach to the pickup line at the tank and going into the fuel pump?


Iowan, if I go to 1/2 line, would the 3/8 pickup at the tank and fuel pump restrict the flow and make it a moot point?
I have not seen a 1/2 fuel tank pickup for a Ford.

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post #7 of 10 (permalink) Old 05-12-2019, 11:22 AM
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Re: Replacing fuel line with 3/8

No, one single point of restriction is better than 15 feet of it.

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post #8 of 10 (permalink) Old 05-12-2019, 06:54 PM
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Re: Replacing fuel line with 3/8

I made my own fuel pickup. Yes yes, it sucked, I had to relocate some things, drill some things and solder some stuff.


1/2inch hard line fuel pickup to the exit of the fuel tank. From there it is -8 to a 100micron filter, to a Carter4600HP electric pump to the engine bay where it hits a regulator. A 10 micron filter and the fuel line hits a fitting where it branches into two -6 hoses, one for each carburetor.
3 years now with no issues.



I do the same thing with transmission cooler lines, just use -6, super super easy to route them wherever I need it. Makes it nice to work on the car or drop a transmission.... you can drop the trans with all the lines hooked up. Disconnect them on the floor, etc.


Depending on your power level -6 may be sufficient and the stock pickup may be fine. I'm making 550hp, and never know what I plan to do in the future so I went the overkill/do it once, route.


If you have never worked with make your own hydraulic fittings or SS braided hose, it takes a little artform and skill to get it perfect. I find thin electrical tape and an angle grinder is the best way to cut it. Keeps the braids tight so you can get the fitting on. Blowing out the hose isn't sufficient, you'll need to do a good bit to clean the hose out perfectly. With an electric fuel pump it was easy to turn it on and pump fuel through it into a filter and put it back in the tank.


Oh and I know it seems like being "cheap" but I used Summit hose and fittings, I've literally run 1/4 mile of the stuff and have not had an issue thus far. The hose and fittings are not as good and tough as the Aeroquip parts I use offshore, but they work sufficiently in a place where they aren't constantly being removed/installed.


Good luck


Drew

1976 F100 390/c6
1963.5 Galaxie 446FE/c6

Last edited by DeepRoots; 05-12-2019 at 06:58 PM.
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post #9 of 10 (permalink) Old 05-14-2019, 11:32 AM
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Re: Replacing fuel line with 3/8

I'm pretty sure my 64 manual shows all the V8 fuel lines on the drivers side and the I6 on the passenger side.

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post #10 of 10 (permalink) Old 05-15-2019, 07:18 AM Thread Starter
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Re: Replacing fuel line with 3/8

I saw this in another forum on this site. It is way above my pay grade.
Does it make sense saying that larger lines don't really help?
Regardless, I think I will at least put 3/8 line in.


Do you need a 3/8" line for that many horsepower? No. Do you need a pump capable of feeding it? yes. I had the Edelbrock pump on my 302 making 375HP, and it feeds it no problem. There are many articles about the capabilities of 5/16" fuel line and how it's been used for most mechanical pumps and engines under 500HP. Many will debate this (especially the people trying to sell you fuel lines!) so do your own research.

The line is the single largest source of pressure drop because it is so long. The 1/4" restriction is very short and the losses are low. The larger the line, the lower the pressure drop at a given flow rate, and the longer the line, the higher the pressure drop at any flow rate. The pump has to suck fuel up the line and once your positive suction head drops sufficiently, you start boiling the fluid in the line and you 'max out' your line capacity. This is even more an issue with impeller (electric) type pumps, but it's true of mechanical ones too.

So first, how much flow do you need for 450HP? Assuming a BSFC of .45 lb/hp/hr, we'll need a minimum of 138lph to supply that. Racers Math 1

Next lets look at line pressure drops @ 138 lph
10 feet of 3/8" line + pressure drop from 3/8" to 1/4": .16 + .03 psi = 0.2 psi
10 feet of 5/16" line + pressure drop from 5/16 to 1/4": .38 + .02 psi = 0.4 psi

So you can see that the line pressure drop is much more significant than the step down to 1/4" at the pump, and that the pressure drop is half in a 3/8" line.

Pressure Drop Online-Calculator

The next thing you have to consider is that when you're accelerating, gasoline is trying to rush back down your line into the tank. Lets say .5G acceleration (120mph trap in 11.3 seconds.) In this case P = rho*g*h = 750 kg/m^3*9.81m/s^2*.5*3m = 1.6psi. This is independent of line size.
I saw this in another forum on this site, that seems to say that large fuel lines are not really necessary? It is way above my pay grade.
Does it make sense?

So the total pressure drop under .5G acceleration for each line:
3/8" line: 0.2 + 1.6 = 1.8 psi
5/16 line: 0.4 + 1.6 = 2.0 psi

Not a big difference. At all.

The vapor pressure of an average summer blend gasoline at 100F is 10.5psi (In Texas. Your state will vary.) Vapor pressure is the pressure at which a fluid starts to boil. So if you are in Texas where the air pressure is 14.7 psi, once you drop the pressure 4.2 psi you start to boil the fluid and you start leaning out. http://www.epa.gov/ttnchie1/ap42/ch07/final/c07s01.pdf Guide on State Summer RVP Standards | Fuels and Fuel Additives | US EPA

You're not close to 4 psi with either the 5/16" or the 3/8" line, so if it saves you trouble and your 5/16" is in good shape, keep it. If it's not, why not upgrade while you're going through the trouble? However, this is only true if everything in the system is 5/16". If your pickup is pinched, your line is pinched, or anything on the tank end is under that, the pressure losses rise quickly, so make sure it is in good shape.

1964 Galaxie 500 351C 4 speed
1971 Pontiac Trans Am 455 HO
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