Holley powervalve

remove the front fuel bowl, remove the metering block from the main body, remove powervlave by putting a 1" wrench on it and turning counterclockwise. Install is reverse of removal. Tis very easy.
 
it just comes off. It goes between the fuel bowl and main body, the 4 5/16" screws that hold the fuel bowl on also hold the metering block on. Once they are removed, the fuel bowl comes off, then the metering block can be removed. It might be kinda stuck to the main body, maybe have to gently pry just a little. You might need to get new gaskets in addition to the power valve in case they break during removal. Normally the good blue gaskets, or the red gaskets, hold up fine.