Tuning with your new rebuilt Quadrajet.

If you have had an old worn out #quadrajet on your car for years and years, chances are you have continued to tune your engine to run as good as it can.
When you put on a nice fresh Quadrajet, your engine needs to be tuned correctly again. You just replaced a major part of the fuel, air, spark, timing combo required for any engine to run. Changing any component requires changes in others to be properly tuned.
Timing is a critical part of carburetor tuning, especially idle issues. Idle tuning is the most difficult section for the Quadrajet due to limited external tuning ability. Idle vacuum pulls fuel through idle circuits, and reduced vacuum from worn engine, large cam and compression or other factors require modifications to the internal circuits for proper idle. Timing plays a huge roll and should be adjusted. Factory settings are a fine starting point, but that is all. They were correct for the engine and fuel available when the specs were created. Most engines have been rebuilt since original, and fuel is definitely different. So your engine tuning needs to adapt. Be prepared to set your timing to the point your engine prefers with your new carb. It may want manifold vacuum for advance instead of ported. It may like a few extra degrees of advance. Be prepared to make changes in your overall tuning for best and proper performance. Changing any component requires adjusting or changing all for best performance.