Power valves on Holley carburetors are usually trouble free, but they do occasionally require replacement. Engine modifications may dictate the use of a different power valve. You may want to change your power valve if you’ve moved to an area that is significantly higher or lower in elevation than your previous residence. Also, power valves may rupture and require replacement if the engine backfires through the carburetor. There usually no need to remove the carburetor from the engine in order to replace the power valve.
Things You'll Need
- Combination wrenches (SAE)
- 5/16-inch nut driver
- Power valve and gasket
- Fuel bowl and metering block gaskets
Remove the fuel line from the carburetor’s fuel bowl. Fuel line attachments vary. The most typical style is a slip-on fitting with a hose clamp. Use a screwdriver to loosen the hose clamp, and pull the hose from the carburetor. Use a rag to soak up any spilled fuel.
Remove the fuel bowl from the carburetor. Remove the four hex head bolts that retain the fuel bowl and metering block using the 5/16-inch nut driver. Using the handle of the screwdriver, tap lightly on the fuel bowl to loosen it, and set the fuel bowl aside.
Remove the metering block to expose the power valve. Again, tap gently on the metering block to free it from the carburetor main body.
Unscrew the power valve from the metering block using a 1-inch wrench.
Install a gasket on the new power valve, and thread the valve into the metering block. Tighten hand-tight plus 1/8 turn.
Using new gaskets, reassemble the carburetor. Attach the power valve side of the metering block to the main body, followed by the fuel bowl. Insert the fuel bowl bolts into the fuel bowl, and tighten the bolts finger tight plus 1/4 turn.
Reattach the fuel line to the inlet on the fuel bowl, and tighten the hose clamp.
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