Howdy, I'm having an issue with the carb on my 1970 C20. I just installed a new 350 with a performer intake, mild cam and aluminum heads. It mated everything to a 700r4 transmission and I'm running a newly rebuilt Carter quadrajet #17057204. On initial start-up I suspected an overly rich mixture based on the exhaust. I pulled the plugs and all of them were black with soot. I threw in a fresh set of plugs, set timing at 12 initial / 36 total. I adjusted the mixture screws all the way down. When initially tightening down the right (driver) side mixture screw, it had almost no effect at all and the engine didn't even bog. Subsequent manipulation seemed to right whatever wrong was present and I was able to get a to a drop in idle. I opened it back up a few turns and then screwed down the left screw. After playing around with the mixture screws, I settled on approx. one and a half turns out on both sides. Exhaust smelled much better and the motor ran and idled great. Upon taking her for a drive and coming to a stop, the idle fell off, the motor began to bog and wanted to stall. I had to feather the throttle to keep her running. This happened each time I arrived at a stop sign or signal. She ran great at speed but I just couldn't hold an idle. I noticed when I was adjusting the mixture screws that both of them seemed loose. In other words, I could wiggle the screw back and forth slightly inside the hole. I sprayed a little starting fluid near the screws with the engine running and noticed a slight bog. Is it possible I have incorrect mixture screws? Is there supposed to be "play" in the screws? I removed the screws and wrapped a little teflon tape around the threads but that didn't seem to have any effect. I'm thinking perhaps a vacuum leak from around the screws. Any suggestions?
