Ok. Now do the same test, except increase the water pressure to the house,and don't create a restriction with your finger.

I know what you meant and you're right. More fuel mass in the line has more inertia so it has more of a tendency to stay put during launch, hence the need for more pressure to move it forward.

Where are you reading the fuel pressure? If you have a regulated pump at the rear, you should still be regulating at the carb, and monitoring pressure there.
You can have pressure and zero flow if reading at the rear, but if you are in a dynamic state(float allowing flow) and you have pressure at the carb inlet you WILL have flow.

You would have more water pressure, but not necessary more flow. The pump will only put out much flow as it is designed to put out at a certain RPM, and the pump puts its most flow out when there is no restriction.
You could increase the voltage (16 volts)to the pump to get it to spin higher and maybe put out more flow.

The original Carter AFB carbs didn't come with that device to pull the floats down, niether did any of the early Carter carbs, 1,2 or 4 barrel WCFBs. I'm not sure exactly when I started seeing those in Carter carb. kits or in the after market over the counter Hi Po AFB and AVS carbs As far as restricting fuel flow I did a test before and after on my old pump gas car with the six pak and the Magnafuel 275 pump and then replaced that pump with a Magnafuel 300 pump. It took the exact same time in seconds to fill a 2.5 gallon jug with all three #6AN fuel lines dumping into that jug I called Magnafuel to complain and they said try using a rstrictor in the lines like the needles and seats are so that would load the pump like the real world, I hooked one line back up to the rear carb and redid the test with the 300 pump on that car, it filled that 2.5 gallon jug up a lot quicker threw(SP?) two lines flowing into it than it did with all three lines free flowing into it No other changes either

listen to thumper.
you can run lower pressure with a larger/better bowl /needle/ seat. A stock holley needle seat/ bowl will not flow enough to keep up with the jets on most engines with a gravity feed under sustained load.

If I understand what Thumper is saying is that there is an added restriction to the flow of fuel through the needle and seat and the bowls. He removes the restriction by putting in a bigger needle seat and better designed bowl. Lowering the pressure, allowing more fuel to enter the bowl.

Which Quickfuel bowls are you referring to? I'm looking for something better than my stock Holley bowls that won't break the bank.

GRAVITY is creating pressure.
Put that fuel jug on the frame rail and see what happens.

Dont have part #`s in ft. of me but it`s a kit that Quickfuel sells for around $105 and comes w/new bolts, nylon washers and gaskets and I try to talk every customer into using em if I can. Just one look at a stock Holley bowl and even the "high end" stuff and you`ll see the wall fuel hits THEN get yer hands on the mentioned bowls, and you will never run a stock one again.........There`s more "science" in carbs than most people think.........

Thumper, is this it? 34-100, comes with aluminum fuel bowls?
It's on their website at $101 and change.........

I have always understood this to be a basic rule in hydraulics. Increasing pressure reduces volume and vice versa. This only remains true while keeping the same orifice.

In our old TS car we would only run 4.75-5 psi with big needle and seat. You don't want to high of pressure because it can get air in the fuel and/or when your floats let fuel in you don't want the fuel on top of the float weighing the float down.

Only way to increase pressure is to choke more witch also reduces flow.
Simple laws of physics.

Doesn't work that way with mechcanical fuel injection. to flow 200 lb/hr takes 20 psi; to flow 400 lb/hr takes 80 psi, so
to get twice the flow takes four times the pressure. Why? If we want to flow twice as much through a fixed hole size, we will have to push twice as many fuel particles through it at twice the velocity, so we will have to do 2 x 2 or 4 times the work. We use the pressure to do this work.

If you want to flow more through an orifice, but keep the pressure the same, then you must use a larger orifice. The flow increases as the area of the orifice increases. Since the area is Pi x diameter squared / 4, the area increases as the square of the diameter, so twice the diameter is four times the area.

Joe

YES........

I need to pull one of the bowls off my QF 750 and one off my Biggs 950HP and compare them. Thanks for the info Thumper.

Post a pic if you can of the fuel entrance for all to see.......

It seems to me that if you have pressure at (just before) the carb, then you have what you need to keep it full. Pressure should only be created from the needle / seat restricting what enters the bowl, based on how much it takes to keep the floats in the correct position. I like the inclusion of the bowl design and needle & seat in this discussion because ultimately it may be more important than the pump. Its the damn, whereas the pump is the river.

I only make a little over 500hp, but FWIW: I run dominator style bowls and .120 needles & seats at both ends of my 830 DP. Some would say overkill, but I think it helps keep the floats in the right position. I monitor pressure right at the carb, and generally I see 6psi @ general running conditions, and it drops to a steady 3.5psi through a run. I run a Carter 110 mechanical pump and stock 5/16 line to the pump, 3/8" from the pump to the carb.

Notable: this past year I had a couple of runs on a real hot day where I watched the fuel pressure guage drop to 0 halfway through the run. I waited for the car to nose over, but it never happened. car ran right on its best MPH on those runs. All I can take from that is that even with 0 pressure, if you have a good flowing system within the fuel bowl, you're probably still okay. (???)

I ran much quicker and faster than the OP at probably as much weight(3350) with a deadheaded Holley Black.
Upgraded the entire system and picked up absolutely zero anywhere.
Save your money Ted for something else.
ETA....... Insuring good and constant adequate voltage at the pump is very important, and overlooked