Fuel in the bowl

[ksa8907]

What if you put a line that will allow the bowl to drain back to the tank. Install a solenoid that will block drainage when the key is on.

Would make for a more automatic way to do the same thing.

[oil pan 4]

I can just burn it off by turning the fuel pump off and driving off that last little bit before parking.
Its only about 100ml of fuel. I think that will only power this monster for about 1/4 mile.
I just don't think there is any way I can get the all down hill slope needed to return the fuel to the tank by gravity.
Driving home I could cut the fuel off, run completely out and just roll into my drive way.
Going to work and the store not so much an option, I could burn off a good portion of it.

[user removed]

Most carbs with accelerator pumps will provide fuel to the accelerator pump until there is nothing left in the float bowl. The idle circuit will also pull fuel until the bowl is empty.

The main circuit relies on the fuel level in the float chamber to operate properly.

The previous statement about float bowl fuel level changing is not correct. the fuel level remains very constant in the float bowl, probably within 1 millimeter since the float level controls the activation of the needle valve that refills the float chamber. That is a very precise control mechanism and it needs to be for the main jet to consistently supply a precise mixture.

You can argue the precision of the mixture all you want, but consider this, fuel economy did not change much when delivery transitioned to fuel injection and Honda's CVCC designs are still top dogs in economy and in their time period were good enough to delay the adoption of catalytic converters.

Precision measurement of the actual amount of fuel in the float chamber, followed by letting the engine idle with the fuel pump shut off will give you a very good idea of the idle consumption, which in most V8s is about .5 gph.

Once you have converted that consumption into a time period that the engine will idle on the fuel in the float chamber and you know the volume of the chamber, you will have that time recorded and can calculate other scenarios using time (to empty float chamber) to calculate the consumption based on the idle consumption time. Half the time twice the fuel and any point above or below the idle consumption time period can be easily calculated as a fraction of X/idle fuel consumption time.

regards
mech

[user removed]

The greatest change in fuel level in the float chamber is when you mash the throttle and use the fuel capacity of the accelerator pump. My guess is it would be less than 10% of the capacity of the float chamber, but the replacement of the fuel by the needle would be almost instantaneous.

regards
mech

[user removed]

As long as you can pressurize a separate container, like a burette, you can precisely measure the amount of fuel consumed.

A small hand pump to pressurize the burette will provide the same fuel pressure as long as you maintain the pressure within specs.

Fill the burette, pump the pressure up to the maximum specs recommended and maintain the pressure with the hand pump. This way you can test anything you want without dealing with float chamber variations that would affect the main circuit operation.

Want a lower float chamber level for lean burn? Let the pump pressure in your burette drop off below the minimum spec and the fuel level in the chamber will drop and you can control that very precisely.

As far as the evaporation you saw when rejetting, ASSuming it was a hot engine, most of the fuel evaporation was due to the heat produced by the engine. Try it over a hot engine, then a cold engine to confirm my statement.

regards
mech

[oil pan 4]

Yes that is what I was thinking.
For testing time or distance with the fuel in the bowl I would hold the gas in the same position as to not add more fuel with the accelerator pump.

Then for fuel burn off I figure I would be pushing the petal down a little here and there just driving normally and maybe more as it ran out of fuel, draining the accelerator cylinder. I figure it would get 50% to 90% of the gas out of the bowls. And therefor cut evap 50% to 90%.

When the carb starts to heat up it starts off gassing through all the little vents, I can see the refraction of light through the gas, looks like a little propane leak.