Idle Mixture Screws

I think there are guys on here who would take a stab at your question with a few more details. Engine size, carb manufacturer, 2V or 4V carb, etc.
 
Assuming it is the stock 2bbl, most people start with 1 and 1/2 and then warm the engine up for a final adjustment.
 
Paul and Russ are correct. But almost all common 50’ s carbs said to start at 1-1 1/2 turns. They get richer as turned out. Only in later years did anything else become common. I recall some where turning out leaned the mixture, but I think that was the emission control days.
 
Gently close both screws and then you want to open them up both 1 1/2 turns, both screws exactly the same amount and then set the idle speed. That's just to get it running. Then you want to turn both screws in or out a little at a time, until the idle starts to drop and then turn the screws back to the highest rpm. Then maybe an additional 1/4 turn out for a little extra fuel for daily temperature changes. To verify you have it adjusted perfectly take a bottle of propane "slightly" opened and run it over the top of the carb. If it's adjusted correctly the propane will have no effect. if it's lean the idle will go up and if it's rich the idle will go down. I was smog tech for 30-years and this was the best way of adjusting the idle A/F mixture.
 
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