FAST Air Fuel Ratio Meter - Popular Carb Tuning Photo Gallery
On the metering block side is a pair of jets that control fuel for the main and secondary. In the center of the metering block is a power valve that controls the idle to off-idle fuel. The power valve should be tuned with the use of a vacuum gauge depending on cam size and vacuum. In general the stock 65 power valve will perform well with 12 inches Hg or higher. If you have a slightly bigger cam with less vacuum at idle then a smaller-numbered power valve is required.