Quadrajet Idle Strangeness
I've installed a rebuilt quadrajet and a Performer intake on my pretty much stock 305 daily driver. The rebuild of the carb was very detailed, even removing and cleaning out the idle tubes and blowing out all passages. The throttle shafts have bronze inserts already installed and I've checked and re-checked the float level, but I still have a strange idle condition.
When the car is warmed up it will idle at a consistant rpm then drop and idle much slower for 5 seconds or so, after which it goes back to the faster idle which it will maintain for about 10 seconds before dropping down for another 5 seconds, etc. etc.
I've attempted to look into the carb while it does this, but I've seen no evidence that the main jets are expressing gas when this happens. This carb has the adjustable part throttle, but adjustments to it have had no effect on this condition, nor has any of the adjustemnts to the idle screws. I now drive the car idled higher than I'd like just to keep it from stalling when it does decided to drop down to it's lower idle speed. I've though maybe the fual bowl is being overfilled by a faulty needle seat or something. But it doesn't figure that it would overcome that within 5 seconds of only idle consumption.
Any ideas? I'm a quadrajet fan and I've owned some great ones, but this has me miffed. I've been trying everything I can think of and nothing seems to help.