How did the pressure carburetor put an end to R-2800 engine cutouts in inverted flight?

The float carburetor makes use of the venturi effect to deliver fuel to the engine intake, and to do so it needs a constant fuel level in the bowl that maintains the desired air/fuel mixture. The float sits submerged when gravity pulls the fuel toward the top of the bowl. Under negative load factor, as in a sharp dive, the float rises toward the top of the bowl. Since its operation depends on gravity, the float stops being effective when the aircraft flies inverted. When inverted, the pump fills the bowl at its maximum flow rate and the mixture becomes extremely rich, which stalls the engine almost instantly.

The pressure carburetor solved the problem: it operates on pressure alone, so gravity no longer has any effect. For that reason it delivers fuel reliably with the aircraft in any flight attitude.

The floatless model is an aircraft fuel control that meters flow very precisely, prevents carburetor ice from forming, and avoids fuel starvation under negative load factor and in inverted flight. Since it works with fuel under positive pressure, it is actually a form of fuel injection.