Originally posted by 6T4Duce:
´68 OrangeSunshine,
My Holley is the #8007 390cfm 4160. It has one power valve in the primary metering block. What is the best method for determining the correct size or value power valve that should be installed for the mods that I have installed on my 194. Diesel Dan posted that there is just one size yet a mechanic in my town has given me a couple different sizes to try. One is a 2.5 and the other is a 6.5. My guess is that I need to install an accurate vacuum gauge, run it into the car so I can determine the vacuum value that it develops when I would want the secondaries to open. Am I on the right track.
When I ran the Holley [I now have an Edelbrock 1404 -- but that's another story) I had a 7.5"Hg power valve in the 390 carb. Or was it 8.5"? My application is a pickup truck, daily driver, manual gears. I'm sorry I'm not up on the technical voodoo end of how to figure at what vacuum pressure [measured in inches of mercury (X"Hg)] you set up the secondaries to kick in at. But basically the later the secondaries kick, the more economical it is on just 2 barrels. I always bribed a more knowledgeable Holley Guru with a 12-pack and handed him wrenches.
In the spirit of self-reliance I now have an Edelbrock. But my Holley ran 25 years before blowing up on me.
I have a Moon Eyes vacuum gauge. I got it back in the day, and it still works good.
