You might try some ' Berryman ' it was often used for such things back in the day. It helps to dissolve lacquer build up. If replacing the ' power valve ' let me suggest you get the Holley model. I recently did some work on my Autolite C5ZF-C and had a bad experience with the rebuild kits version and the the NAPA version as well. The rebuild kits call it the economizer valve. Brian