One of dozens or hundreds of ineffectual "gas saving" devices based on marketeering and handwaving and gross misunderstanding (or deliberate disinformation) about how engines work. And that nice, big glass bowl looks like an excellent way to create a serious fire hazard under the hood.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Varying the float fuel level will make the fuel mixture leaner or richer depending on if you lower or raise it.........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

In the carburetor, yes, but this is an external device that claims to reserve the "waste" or "extra" fuel in the carburetor.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.