Editing How to rebuild a Rochester Quadrajet 4MV carburetor (section)
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====Pulloff orifice==== Once that's squared away you can go about quickening the opening rate by enlarging the pull off orifice. One way to do this to go very large on the factory-installed orifice, then solder the opening shut. From there, enlarging the orifice is as easy as using a small numbered bit in a pin vise. If you go too large, a touch w/a soldering iron will close it back up. And plan on going too large during the tuning of the orifice size, because you will keep enlarging it until you go too far and get a bog, then you back up to where it was best (just like the opening amount of the air valve). Some pulloff diaphragms have a 90 degree bend in the vacuum tube. If there is enough length before the bend, the 90 degree can be cut off in order to reach the orifice. If not, the tube can be carefully ground down at the 90 degree bend enough to access the orifice with a drill bit, then enlarge the orifice oversize as explained above. Reseal the tube and tune it by changing the orifice size at the soldered over tip of the vacuum tube.
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