Got a question about charger with rich idle

[69wannabe]

My charger run's great, cannot beat it driving around. Smooth acceleration no bogging or hesitation. Stab it and it goes fine!!! The only thing that bothers me is when it idles it has a rich smell and will burn your eye's pretty quickly. It's a 493 ci with approx 10 to 1 compression cast iron heads with the bigger valves, Eddy RPM intake and 850 double pumper holley carb. The cam is a XE284 comp cam and the ignition is a firecore plug and play with a mopar chrome box and msd blaster 2 coil. The timing is 18 initial and 34 total and the plugs are NGK 5670-6's. I had jetted up the carb a couple of sizes awhile back since it had a stumble off idle and after the jet swap the stumble is gone and the plugs look better too. That is the only changes to the carb I have made. I may need to swap down a size on the power valve from a 6.5 to a 5.5 but it has a healthy idle just seems rich. My idle speed is set at 900 rpms and last time I checked there is just a small square showing on the front throttle plates and the back ones are closed completely. Besides this small issue the car runs like a champ. I do not have a A/F gauge to read the ratio I just check the plugs often to see how they look. Just wondering what I may be able to do to clean up the idle smell a lil bit... 

[Paul G]

I have the same problem, if we even consider it a problem. A rich idle is sometimes unavoidable with a performance engine build. That was the conclusion of my research. You can try to lean out the idle mix screws just a little, that will help a little. The engine will idle a little rougher when you do that but it is no big deal.

I do have an A/F ratio gauge. My engine has the smoothest idle at 12 to 1. I leaned it to 12.3 to 1, just by turning the idle mix screws in a hair, like an 1/8 turn each. The stink was less, the idle got just a little rougher but acceptable. 

[69wannabe]

That's about all I can figure myself, I know when the engine is cold it is going to be rich until the engine warms up and get's to normal operating temperature. It still seems to be smelly tho... Maybe just the nature of the beast as they say. 

[Mebsuta]

They all smell like a big lawnmower.  I think that's just how it is until you start adding air injection, catalytic converters and all the stuff for emissions. 

[NHCharger]

I have the same problem. I have a built 440 in my 68 and when I first got it running last year the fumes at idle would make your eyes bleed. After a lot of fiddling, swapping out the IAB's and some adjustments I ended up drilling a 1/16" hole in each butterfly. This allowed more air at idle and helped get rid of 75% of the fumes.

[ZekesGarage]

I've noticed that with some big cams and other modifications, a lot of engines need a bit higher idle speed. Because of this throttle plates may have uncovered the idle transition slot, and it's pulling fuel through the main jets instead of just the idle circuit.
You can verify this by turning your idle screws all the way in (count the turns) and see if it still runs. I've had to fiddle with the timing and idle mixtures to get this cleaned up on some engines so that the throttle plates could be closed enough, but like was said earlier, sometimes that's just how it is.