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Posted this problem several times, without any significant help. I have a new Edelbrock 1404 (500 CFM) carb on my 302. It runs extremly RICH, and I cannot lean it out. I have played with the mixture screws, and while they have an effect on idle quality, it is always too rich, and the carb loads up. On acceleration, or cruise it is fine. If I let up on the gas for a second or two, as if to coast, or shifting gears( 4 Speed) when i step on the gas to resume, it stumbles for a split second as if the carb is loaded up. Vacuum is about 19 " at idle and is steady. I don't have a timing light, but it seems O.K. is this an issue at idle?? Electricals seem fine. I appreciate previous responses, none were helpfull. Any carb experts?? I need help with the rich idle problem.
 

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two conditions are most likely to cause an over-rich indication

carb; (that was a good choice of carb size, btw)

is there fuel trickling out down the carb throat (not normal)
are both front idle screws no more than 2 turns out?

ignition

timing usually doesnt cause an over rich......at 19" vacuum, it shouldnt be too far off (but checking it is never a bad thing)

points, condenser, coil, wires, voltage to coil
 

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they can cause the appearance of a rich idle....too much fuel or not enough spark
 

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What type of fuel pump are you using?Fuel pressure higher than 6 psi will raise the float level and cause an over rich mixture. How did it run before the carburetor was changed?A weak ignition can make an engine run rich.Check the voltage input at the coil(it should be about 9 volts once it warms up,with the engine running).You may have one or more problems contributing to the condition.Do some more checking and let us know what you find..
 

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Hi overlap camshaft will idle rich, Overly ported (intake port) heads, stuck economiser valve, plugged air bleeds, too much fuel pressure, soaked or filled floats, etc... (Short list)
 
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