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Fuel line as a "reservoir"

mala

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My current set up is:
Tank sending unit is a stock 3/8" ( New is 1/2" )
Fuel line is stock 3/8" ( New is 1/2" )
Mechanical fuelpump
From pump to carb is an-8
And I have a little return line 3/16 with a jet back to tank, return is located between pump and carb.

This has work ok so far, but I was little concern that this not fed motor on a 1/4 track.

So I bought a new tank sending unit that is a 1/2" ...... Or should have been a 1/2" but the tube is flattened in the bends. My thought was to use the tank sender anyway and a 1/2" fuel line to the fuelpump.

Now the Q: When I stage on track and the pump "filling" the whole system.... Can I use my bigger fuel line as a "reservoir" and have it to fed my pump for a couple of seconds longer here?

Thanks!
 
Not sure what you mean, but how fast does the car go?
 
I wonder if the bigger fuel line (more area) can fed the fuel pump longer even if the tank sending unit maybe is restricting the fuel line.

On the 1/8 it has go 6.94 - 100 mph weight is 3860.
 
My current set up is:
Tank sending unit is a stock 3/8" ( New is 1/2" )
Fuel line is stock 3/8" ( New is 1/2" )
Mechanical fuelpump
From pump to carb is an-8
And I have a little return line 3/16 with a jet back to tank, return is located between pump and carb.

This has work ok so far, but I was little concern that this not fed motor on a 1/4 track.

So I bought a new tank sending unit that is a 1/2" ...... Or should have been a 1/2" but the tube is flattened in the bends. My thought was to use the tank sender anyway and a 1/2" fuel line to the fuelpump.

Now the Q: When I stage on track and the pump "filling" the whole system.... Can I use my bigger fuel line as a "reservoir" and have it to fed my pump for a couple of seconds longer here?

Thanks!
Smokey Yunick was famous for using a fuel line as a reservoir... Smokey Yunick Was NASCAR’s Greatest “Cheater”
 
Smokey Yunick was famous for using a fuel line as a reservoir... Smokey Yunick Was NASCAR’s Greatest “Cheater”
This is well known everyone ups fuel line size. Remember most factory stuff was built on minimum size to save money. Some of us heavy mechanics have been even running larger fuel lines then into a fuel cooler. Data has shown less pump problems and less air in line problems. Just my 2 cents
 
A large volume fuel filter between the pump and carb does the same thing, acting as extra volume available on acceleration. Since you have more volume to move, an electric fuel pump mounted at the tank would be the best setup.
When you have more volume, you also need a pump designed to move more volume.
 
The trouble with a big huge fuel line, and a mechanical pump, is that the mechanical pump DRAWS fuel. At launch assuming a near 1G launch, the fuel in the line Doesn't move, so the pump can't draw any, and starves. If you have enough reserve in the fuel bowlsto keep the engine running till the g-forces diminish, the pump might pick up enough for a quarter mile pass, or it may not.
An electric, at the back of the car, has a much better chance of PUSHING the gas against the g-forces trying to keep fuel away from the engine.
Now if you have to keep the mechanical pump, an auxiliary fuel tank up front might work. Remember the sixties gassers with the Moon tank in the grill?

Bottom line: imo, 95% of fast cars use an electric pump.
 
Why not have the return line after carb? Why bleed off fuel before where it's needed.
 
My current set up is:
Tank sending unit is a stock 3/8" ( New is 1/2" )
Fuel line is stock 3/8" ( New is 1/2" )
Mechanical fuelpump
From pump to carb is an-8
And I have a little return line 3/16 with a jet back to tank, return is located between pump and carb.

This has work ok so far, but I was little concern that this not fed motor on a 1/4 track.

So I bought a new tank sending unit that is a 1/2" ...... Or should have been a 1/2" but the tube is flattened in the bends. My thought was to use the tank sender anyway and a 1/2" fuel line to the fuelpump.

Now the Q: When I stage on track and the pump "filling" the whole system.... Can I use my bigger fuel line as a "reservoir" and have it to fed my pump for a couple of seconds longer here?

Thanks!
I think a larger than needed cross sectional area of a fuel line on the suction side where you are trying to suck fuel against the direction of acceleration is not going to help
 
Gas weighs more on acceleration, or it acts like it. Can you lift 20 pounds easier than 50? To big a line and you need an enormous pump to ‘push’ that fuel forward (heavy) leaving the line. So use your reservoir in FRONT of the carb so inertia and pump pressure will force it into the carb, keeping the 3/8” line or no more than 1/2” line. a Holly Blue or black will do the job up to 600 hp. Think of one more thing, the size of the needle and seats are small compared to the amount of fuel in a 3/8” line. Test have shown that 3-4 pounds of pressure is all that’s needed for a 1000 hp engine (pumps and tank in the front)
 
Thanks for your answers, you have all good points her.

This is 90% streetcar and just se track time a couple of times a year.

I know it be so much easier with a electric fuel pump, but I like the simplicity with a mechpump and stock fuel line setup.....
So I just se if I can "band-aid" my current set up with a bigger tank sender and line. I think my pump can handle the bigger volume.

Fran Blacker: I put this together with a streetcar in mind..... but it been more focus on a track slip nowadays. Yes, I maybe move my "bleed off" after the carb.
 
Have you confirmed that you even have a fuel starvation problem?
 
I have a not thats says 6,5 psi at idle an 8 psi at 3000 rpm. If I remember correct :rolleyes: I had 2-3 psi at finish line in a 1/8 track then. But I don't know if I had my current camshaft at the time, shift a couple hundreds later now. Next time at the track I mount a gauge and confirm.

This was most if I goes to a 1/4 track I am a little concern about the fuel supply.
 
If you're really really stuck on the mechanical pump idea,, could you just mount one at the back? Maybe an eccentric on the yoke, like some guys do with an alternator.
 
I wonder if the bigger fuel line (more area) can fed the fuel pump longer even if the tank sending unit maybe is restricting the fuel line.

On the 1/8 it has go 6.94 - 100 mph weight is 3860.

If the sending unit is the restriction a larger line would not result in more flow.

Put a 1" fuel line on the car with a 1/16th sending unit feeding it and the pump will struggle to draw through the tiny initial inlet.

You could put a 1/2" sender and fuel line on the car and have it result in no more volume. I don't think the pump fittings and internal check valves could match the ID of that line but maybe I'm remembering incorrectly.

I would think to get the most out of the pump you would do better with a regulator on the return line rather than a jet.

(because you're always bypassing some fuel which is not what you want as you watch the pressure drop)
 
Pumps inlet hole is 31/64 and has a AN-10 fitting, outlet hole is even bigger and has a AN-8 from start.

Good point with a regulator after carb, I take that in my plans. I gonna see if I can "straighten" out tank tube or replace pices of it so it maybe gets better.
 
Update!

You have all being right.

I have moved my "bled off" line from between mech pump and the carb, now mounted to after the carb. When driving to the track it had 7-8 psi.

Did a couple of passes on 1/8 track...... Fuel gauge showed 1-2 psi at finish line, same result with the bled off / return line blocked off. So the mech pump is not able to suck against the G-force I guess.

So I guess I need a electric fuel pump. I was thinking of a Holley "red" pump mounted near the fuel tank to push fuel to my mech pump just when doing track time. Street driving its off and just going on the mech pump.

Q: Is this a reliable setup for a street&strip car? Is the "red" pump good enough for this or is there a better choice?
 
Just curious how much gas was in the tank at the track? If your pickup is uncovered electric pump won't help.
 
Red is low pressure, blue or black is higher pressure. attach a momentary switch on the carb so when the pedal is pushed to the floor it activates the pump. This keeps the pump from running all the time and only when needed. Is your battery in the front or trunk. Determines how the pump is energized.
 
Had 1/2 or little more in gas in the tank, I think it cover the pickup.

I was thinking of the red one just because I could activated with a switch when I rolling in to the water. I have a Holley Black pump on the self so I am all ears her.

Battery is in the trunk.

Im looking in my old gas tank and thinking of welding a sump an a 8-an in that one, and let the sender just reading the gas level.
 
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