Building 550-600 hp mostly strip motor. I know 5/8" aluminum fuel line is overkill, but I'm sure this won't be the last motor in the car. Already have Holley Blue fuel pump, and I'll be using it. Hope to run fuel system as follows: Earl's 85 micron or Aeromotive 100 micron filter before the pump with -10AN feed line, 5/8" Aluminum line to 10 micron canister filter, then 5/8" line to Holley Blue regulator which I'm not all that thrilled about using, -8AN line from regulator to Y-block, -6AN line to each carb. I'm not to crazy about using a deadhead regulator, and may eventually change to a bypass style, as there's currently 3/8" aluminum line on the car (originally used as fuel line) which I should be able to use as a return line. Are there any drawbacks to using an obviously oversized fuel line? Any other problems with the system?

 

some draw backs are:
-difficulty in plumbing (easier to kink)
- if you 60 ft hard enough the fuel can actually stall in the line because of the increased fuel mass- though just on pro-stock style lauches.

btw- I believe prostock car use 1/2 line

with this info I still choose 5/8 for my supercharged application
call me a hypocrite

 

I may go forced induction in the future, that's why I'm considering the 5/8". I don't really see it as being a hindrance with a NA 550hp motor, but I could be wrong. I'm not quite up to pro stock 60 ft's, but I was concerned about a pressure drop at WOT if the Holley Blue pump is not strong enough to keep the line full of fuel and pressurized, although I doubt this will be the case.

 

A 3/8" aluminum line will support 800+ hp. 1/2" is adequate for most all applications. A large line has less fluid velocity and laminar flow keeps the friction down. Laminar flow means the closer to the center of the line you get the faster the fluid is moving, like a river. The weight of the extra fuel in a large line does have some inertia however. Mortal men's 60ft times are not a problem on a higher pressure dead head system such as yours. A return system is best of course for many reasons. For a high G launching drag car the fluid is moving with a return system and not sitting still on the launch pad while the car accellerates away from it.
This is a for instance and I am not making a sales pitch, but just an example: Our 11203 SS series carb pump makes enough volume for over 900 hp with a return system. 3/8" pipe fittings, same as your holley. A return system provides full pump volume to the demand without going through a restrictive cartridge first. The excess volume is metered back to the tank to maintain set pressure at all times. You could easily figure that a return fuel system will allow for 100+ more hp potential than the same pump dead headed. Pump flow decreases with pressure.

Today's pro stocks run front mounted cells so accelleration actually enhances fuel delivery somewhat. Some are experimenting with very high pressure efi pumps and the regulating that down and on to a traditional dead head regulator. They are actually running 2 regulators. For what its worth I feel it is a waste of time, just an exercise, and a case of "monkey see, monkey do".

 

You hit it on the head with my concern about the inertia of fuel in the line upon launch. Considering two tube sizes, the one with the larger cross sectional area will hold more fuel, and consequently more mass for a given length. So if you consider Force = mass x acceleration, where the acceleration remains constant, the mass to be accelerated increases, and therefore, the force required to accelerate the fuel would be increased. Thus, more of a pressure for the pump to work against with a larger line. So I guess my question would be like something as follows: Now for any given horsepower level, the volume of fuel needed to achieve that horsepower level would be the same no matter which size line I'd use. So to achieve the same amount of flow per unit of time with a smaller line would require a higher fuel velocity. To achieve that higher velocity would require more pressure. Would I be better off to use the smaller line which would consequently increase the load the pump had to work against, or use the bigger line with a smaller pressure? So in the small line situation the pump would have to provide a higher pressure, and in the large line example, the pump would have to provide a lower fuel pressure, but also fight against the higher inertia of the increased mass of fuel in the line. Seemingly, the effect of inertia on the pump in the large line example would be much less than the effect on the pump of having to produce an increased fuel pressure. Any thoughts?

Incidentally, how do you feel about continuous duty use of the A1000 pump?

 

Yes, you are doing a good job thinking it through, but....I'm going to hopefully help you out. Dealing with your combo, and a potential upgrade, remember that you are talking about a very brief accelleration force on your car that diminishes rapidly. Your fuel bowls are going to carry you through this period of maximum accelleration where any potential flow stall is occurring. Actually on a dead head system there is no real flow until the demand is there. Now consider a car with a 1.0x 60ft time. This averages out to 2 G's on the horizontal fuel system. Plumb the system in 1/2 id and 5/8 id line.
First let's say 12 ft of 1/2" line. That's .76 pounds of gasoline, multiply by 2 for the g force and your get 7.74 psi (.500 orifice) of gasoline working against you. This is an average. At the transbrake or clutch release the force will be higher, briefly.
Now the 5/8" line: 2.37 pounds of gasoline @ 2 G = 12.07 psi (.500 orifice) due to the larger area and same orifice size I pulled out of a hat.

Please keep in mind I am merely a salesman at my company and not an engineer. I am an experienced enthusiast though and this should help demonstrate the effects of line size. As the pump orifice goes up in size, like you would typically have with a -10 line the effects are less dramatic as you have a more balanced area on both sides. I should have used a .375 orifice as that would be more likely with your holley pump.

I use the A1000 in my carbureted '69 camaro. It is rated for 2500+ hours of continous use and it should provide you with an excellent service life.