correct power valve on a Demon carb?

[nova]

What is the best way to make sure I have the correct powervalve for Demon carbs on my Small block 302's?

[DeputyDawg]

If you have a vacuum gauge get it out and hook it up. Start the engine and see how much vacuum you have at idle, then devide that number by 2 and that will get you real close on the power valve. Example, if your gauge reads 9 then you would need a 4.5 power valve.