This is interesting. In the cavity where a plastic cup usually resides (think 75-76 APT models), there is a copper bellows???( I'm guessing,) with a metering rod on the bottom that goes into a jet. Also, next to a primary jet there is another jet. What is their purpose? This carb is going on a 2000 Vortec 350. Nothing special, just a 5000lb. truck. 2.73
rear, 4900 lbs., old man driving. Anyone guess what the MPG potential is?