carb problems

If your rebuild kit supplied you with a Quadra-Jet base gasket(almost always a brown thick gasket), you will loose the idle circuit. This is because the primaries on the 850 cfm carb that you have are larger than the opening in this area of the gasket. The fuel/air mix will 'hit a wall' so to speak, thus killing the idle circuit. Your base gasket should be a black gasket, David.