1955 4000 Teapot power valve

[zeroroadkill]

Question: How does the economizer diagram operate? Does vacuum pull the diaphragm up compressing the springed plunger causing the power valve to close and when vacuum drops (WOT) does the spring force the plunger to push the power valve open allowing more fuel?

If so, with the engine off and no vacuum holding the plunger up, would the power valve be open draining the fuel bowl into the intake?

Is the power valve routed into the tubes on the backside of the float bowl? Don’t have the diagram handy.

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[Hernando Muñoz]

I thought it was the opposite, hence, the name of Power Valve... it allows more fuel into the engine when you open the butterfly valve wide open for high power (and therefore the high side of the carburetor). When the power valve "closes" pulled by vacuum, it allows fuel trough its side "windows" or "vents". Then, when you cut the vacuum, the valve "opens" and the side vents are closed now, and the carburetor only works out of the main jet at the lower side of the carb. No fuel should go through it at low vacuum as it has a sealed diaphragm. It it ever happens (a leak), then the diaphragm is cut open and the valve needs to be replaced.
Check this video form a real expert:

 

[Hernando Muñoz]

Revisiting, when the butterfly valve opens (full throttle applied) the vacuum is LESS and hence, the valve opens to provide MORE fuel. When the vacuum is HIGH (at throttle closed, no gas to the engine), then the power valve CLOSES, and less fuel is provided to the engine.

 

[zeroroadkill]

I’ll have to get the 4000 diagram out but if I recall correctly the economizer is a spring loaded shaft with a rubber diaphragm on top it bolts into the top of the fuel bowl cap cover and is operated by vacuum. The power valve sits below in the bottom of the fuel bowl, and is also spring loaded. at full vacuum or idle, the power valve economizer diaphragm is pulled upward against its spring and relieving the pressure on the spring loaded power valve shutting it off. At WOT, vacuum is lost and the economizer piston drops due to the spring pressure and pushes on the power valve, opening it and releasing more fuel for acceleration. I believe this is how it works on the Holley 4000 teapot carburetor on my 1955?
If I’m mistaken, please correct my assumptions!

• Power valve, or power piston. The economizer diaphragm should get pulled up at idle, there needs to be vacuum going to the diaphragm.

 

[Hernando Muñoz]

Revisiting, when the butterfly valve opens (full throttle applied) the vacuum is LESS and hence, the valve opens to provide MORE fuel. When the vacuum is HIGH (at throttle closed, no gas to the engine), then the power valve CLOSES, and less fuel is provided to the engine.

 

[zeroroadkill]

I believe the video provided is not the 4000? I just expounded on your example.

 

[Hernando Muñoz]

Yeap, it is not a 4000, but the Power Valve works identical on every carburetor that has one or two. The point is that when there is NO vacuum (full throttle) it provides more fuel. When there is MUCH vacuum (no throttle) it does not provide extra fuel. And the original question (and concern) was "if it will flood the intake manifold at idle", what is not correct, as long as the gasket and the diaphragm are in good shape.