No power valve?! Does this work?

[Dirtmod13]

Just heard this for the first time, Guys running with no power valve and larger jets. How does this work and any other info would be appreciated. Thanks

[Hurst390]

More of a drag racing thing...it works great if your wot all the time...on a circle track car it will be rich part throttle...

[SLM98]

Works good on a Rochester 2 barrel . Have to richen up 4-8 sizes

[26-62 racing]

The idea of a power valve is to open at low manifold vacuum, when the power valve opens it allows additional fuel to flow through then power valve circuit to eliminate the lean condition in the motor that cannot be controlled by the main circuit in the carburetor. The main circuit is controlled by the jet size. Turning through the corner with a higher manifold vacuum the power valve is closed. Coming out of the corner with a wide open throttle, as the manifold vacuum drops the power valve will open. The number on the valve is where it will open, example 6.5, at or below the valve is open, above that number the valve will close. Down the straight away as manifold vacuum rises the valve will close. What this means is when the engine is calling for more fuel the power valve will supply that need. If the power valve is not there the motor will be in and out of a lean condition every lap, which is hard on the motor when it lean out. With the power valve is removed, and you increase the jet size you are making the motor run rich to cover up a lean condition that you just created by removing the power valve. It is their to provide extra fuel when needed, why try and out think the carburetor designers when it has been the since the beginning. I would just leave it their to do it job to provide more fuel when needed.

[fastford]

The idea of a power valve is to open at low manifold vacuum, when the power valve opens it allows additional fuel to flow through then power valve circuit to eliminate the lean condition in the motor that cannot be controlled by the main circuit in the carburetor. The main circuit is controlled by the jet size. Turning through the corner with a higher manifold vacuum the power valve is closed. Coming out of the corner with a wide open throttle, as the manifold vacuum drops the power valve will open. The number on the valve is where it will open, example 6.5, at or below the valve is open, above that number the valve will close. Down the straight away as manifold vacuum rises the valve will close. What this means is when the engine is calling for more fuel the power valve will supply that need. If the power valve is not there the motor will be in and out of a lean condition every lap, which is hard on the motor when it lean out. With the power valve is removed, and you increase the jet size you are making the motor run rich to cover up a lean condition that you just created by removing the power valve. It is their to provide extra fuel when needed, why try and out think the carburetor designers when it has been the since the beginning. I would just leave it their to do it job to provide more fuel when needed.

im glad I didn't have to type all that, very well explained 26-62

[mclendon]

had a guy tell me on a 3310 vacuum secondary, remove the rear p/v and jet up ...

[DaveBauerSS6]

had a guy tell me on a 3310 vacuum secondary, remove the rear p/v and jet up ...

The first two versions had rear power valves, all the later had plates ( no PV). 26-62 said it well. Most carb manufacturers build 3 stage main metering systems. By removing one stage you are going backwards. I love my VDL for that reason.
15 years ago I was laughed at for mounting a vacuum gauge to the window of my hobby stock. Now I trouble shoot their carb problems.

[mclendon]

should the p/v be the same on front and back ? 74 jet front....76 jet in back

[DaveBauerSS6]

Run the same on circle track.

[mclendon]

this is a 3310 vacuum secondary with metering block on rear w/o a/f mixture screws