Heres something that I discovered while rebuilding a q-jet recently. After seating both idle mixture screws and adjusting them out the same number of turns, I flipped the baseplate over to observe how much the mixture screws were sticking through the holes and I noticed that they were out different amounts. I had already drilled the holes to the same size so I removed both screws and measured the overall length. What I found was that one screw was appox. .035 longer than the other. I began to check the other carb mixture screws I had and found that they normally vary from .005-.007 difference. After looking through some spare screws, I found 2 that fell within the .005-.007 range and used them instead. This fixed the problem. I could see where this could cause big problems trying to adjust the carb idle mixture accurately.
