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I need some help with adjusting my carb. I have tried the classical approach...tighten mixture screws, back them out 1-1.5 turns and then slowly adjust until the motor starts to stumble, ect. I know that on some carbs, the direction you turn the screws differs. I have tried both ways and nothing seems to help. This is my first encounter with carb problems so I am not sure if the mixture is LEAN or RICH. Here are the details:

350 SB Chevy, 600cfm Holley (I think its a newer one it has gray bowls)
Black soot in the exhaust.
Strong exhaust odor
Fills garage with hazy blue-ish "smoke"

the car seems to be running fine, but because of the excess exhaust discharge I must be RICH or LEAN. Any suggestions out there???
 

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Start by checking your timing and adjusting it. Set your idle speed to where it should be (usually around 700 rpm), then adjust the mixture screws to get maximum rpm, then back off both screws evenly to get a total 20 rpm drop, reset your timing and idle speed. This is a lean-best method. Hope it helps! John
 

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Hey 1,
Tired69 is right on; do what he says using a vacumn gauge. Look for the highest vacumn reading at the correct idle rpm. Much easier that doing it by ear. mgg
 

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If you can't stall the engine by turning the mixture screws in then you have a vacuum leak and it's best to bebuild it. Mixture screws are marked with a tag if you turn in (clockwise to richen). If it's not marked then lean is clockwise and rich is counterclockwise.

Mark
 

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Have you checked the floats? If they are too high you will never be able to lean out the idle. Even if this carb is new they are often not adjusted properly.
 
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