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TECH TIPS
Blocking Off a Power Valve
Power valves are used for off idle /transition enrichment. They are an efficient way to enrich a motor when it needs it without having to over jet it.

If you are running a high performance motor that goes from idle to wide open throttle and thatís all it does and you want to block off the power valves you typically need to enlarge the main jet. The amount you increase the size of the main jet is relative to the size of the power valve channel restriction. But it is safe to raise the main jet size between 5 and 8 sizes. Sometimes, depending on engine requirements it can be as high as 10 sizes. Precision testing can be performed with an air fuel ratio gauge or on a Dynamometer

For example, a 4bbl carb with a primary power valve and a 72 jet would require a change to 77-80 jet if you were to remove and block off the power valve. And the same would apply if there was a power valve on the secondary side.

Simply unscrew your power valve and using our part number pv25620, thread the block off plug in using the new gasket that comes with it. Make sure that when you thread the plug in that the gasket seats properly on the block off plug.

Do not forget to change the main jet to accommodate the change that you just made. Our part number for main jets is mj2240 then select the size that you need.


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  • SETTING AN AUTOMATIC CHOKE
  • Camshaft Changes and Rough Idle
  • Blocking Off a Power Valve
  • Proper Carb Size Selection
  • Vacuum Leaks
  • Checking the Holley Float level
  • CARTER COMPETITION SERIES AFB SPECS
  • HOLLEY DOUBLE PUMPER 4150 CARB SPECS
  • EDELBROCK CARBURETOR CALIBRATION SPECS
  • HOLLEY 4150 HP SERIES SPECS
  • Adjusting Holley/Demon mixture screws
  • EDELBROCK VENTURI SCREW
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    HOLLEY CARBURETOR VACUUM SECONDARY DIAPHRAGM
    Stock #: D35747
    Only $2.99!

    WEBER CARBURETOR AIR FILTER ELEMENT
    Stock #: FE-1005f
    Only $7.50!

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