Quadrajet

==Power enrichment==

==Power enrichment==

Most Quadrajets use a vacuum operated piston (the "power piston" or "PP") to move the primary metering rods to control the air/fuel ratio, allowing the mixture to be lean under low load/high vacuum conditions and rich during high load/low vacuum conditions.  A less-common, early version uses a linkage driven off the primary throttle shaft to mechanically move the power piston.  There were also two Q-jet designs used mainly in 1975 only, that used an auxiliary enrichment system in addition to the primary PP system. There are two types of auxiliary systems: one has an aneroid "bellows" that responds to barometric pressure changes; it used no vacuum or power piston to operate it. The other uses a vacuum operated PP like the primary PP, but it differs by using only one metering rod and one jet to feed both sides of the primaries. These were abandoned soon after they were released; it was found the primary PP system could be tailored to meet the requirements without the added complexity of the auxiliary system. Other changes came on-line in that same era, info on this can be seen at [[Quadrajet#Variants|Variants]].  

Most Quadrajets use a vacuum operated piston (the "power piston" or "PP") to move the primary metering rods to control the air/fuel ratio, allowing the mixture to be lean under low load/high vacuum conditions and rich during high load/low vacuum conditions.  A less-common, early version uses a linkage driven off the primary throttle shaft to mechanically move the power piston.  There were also two Q-jet designs used mainly in 1975 only, that used an auxiliary enrichment system in addition to the primary PP system. There are two types of auxiliary systems: one has an aneroid "bellows" that responds to barometric pressure changes; it used no vacuum or power piston to operate it. The other uses a vacuum operated PP like the primary PP, but it differs by using only one metering rod and one jet to feed both sides of the primaries. These were abandoned soon after they were released; it was found the primary PP system could be tailored to meet the requirements without the added complexity of the auxiliary system. Other changes came on-line in that same era, info on this can be seen at [[Quadrajet#Variants|Variants]].