[Tom Vaught]

So now we talk about #12 & #13

12 & 13) "If you have a carburetor older than 1992 (or you have experienced an extreme backfire) and expect a blown power valve, use this simple test.*TEST: At idle, turn your idle mixture screws (found on the side of the metering block) all the way in. If your engine dies the power valve is not blown."

As was mentioned in a earlier post, you can take the jets completely out of the metering block and the idle will not change because the Main Jet Orifice is much larger in area vs the Idle Feed Restriction which supplies fuel to the Idle Circuit.

So turning in the idle mixture screws all of the way does nothing to prove whether the Power Valve is damaged (Blown) or not.
Another Old Wife's tale that will live forever.

Holley added the tiny spring and ball to the base plate, as the story was going around that if you have a Holley carb, and the Power Valve blows, the Power Valve will allow the engine to syphon fuel from the carb bowl and the fuel will then hydra-lock the engine and damage parts.

Holley Engineers knew that this was Bull**** BUT in order to sell carbs they put in a "anti-backfire" check valve system in the carburetor throttle baseplate.

I have run Holley carbs for over 50 years and have NEVER HAD a single occurrence of a Blown Power Valve.

So a second line item in the article is suspect.

Tom V.