Holley Aluminum Metering Block. Great for Street Strip custom Calibrating. This all Cast Aluminum metering block comes with Threaded idle feed channels, and power valve channels. The Emulsion circuit is NOT threaded. 3 emulsion holes on each side. There is a provision for a timed vacuum pipe on the side of the block. This block will come unassembled but with the vacuum tube, 2 idle feed restrictors(.025 pilot hole), 2 power valve channel restrictors(.025 pilot hole), and 4 metering block plugs.