Try it with them all out 1.5 turns from lightly bottomed, see how it works. If it blubbers, turn them all in an equal amount until it stops. If it coughs, turn them all out an equal amount, until it stops. Play with it, see how it does. If you get some specific issue, tell us about it, maybe we can help. The point is to make sure they're all the same number of turns out from lightly bottomed out. That means, tighten them so they just seat the screw, don't apply any torque to them. Then unscrew them (counterclockwise) the same number of turns, aiming for between 1 to 3 turns out. And do all this adjusting after it's warmed up.
Fouling plugs had badly 1st Gen 392 Hemi, electronic ignition, no MSD box. It caused more issues, than it was worth.
Check to see if the metering rods are being ****ed down at idle. If your care full you can do one at a time.
I know it is caused because it is running too rich. Very difficult adjusting rear carb. I know needs to be lean. I was considering adjust back carb to lean (in), then do fine adjusting on front carb only???
You could try that. But if they all need to be out less than half a turn, then something else is wrong. Did you set the float levels correctly? The chokes are both fully open?
With it warm and idling, look down the throat of each carb to see if any fuel is dripping out the venturi's. You should see no fuel, the carb throat should be dry. If you do see fuel, it either means the fuel level is too high, needle and seat is leaking, or the throttle plates are opened too far causing the fuel to be pulled from the venturi's.
First off are you running them 1 to 1 or progressive ? Which model edelbrocks are you running ? Loosen the screws on the 2 little top caps and rotate the caps just enough to see the metering rods without them being able to come out. Start the car and watch the metering rods, blip the throttle, they should rise and immediately go back down when the vacuum comes back. You might have to go to a softer spring in the metering rods... ...
Put a vacuum gauge on it and adjust for highest vacuum reading, do front carb then back carb, then repeat process again. On dual carbs repeating the process is important because one carb will effect the other. After you've done it with the guage a hundred times then you can do it without the guage using your ear to listen for highest rpm and your hand to feel for the smoothness of the engine.
Keep in mind that the screws you're adjusting will only affect the idle mixture. They will have little or no effect on the rest of the fuel curve.
Thanks everyone. I am going to try reagjusting using my va***n gauge, to get as lean as possible with the highest va***n.
I haven't used a vacuum gauge to adjust idle mixtures for decades, and I've put hundreds of thousands of miles on carb equipped vehicles in that time. But don't listen to me
Edelbrock carburetors should have a small vacuum port on the front drivers side. When at idle with a vacuum gauge on that port you should read no vacuum. That is ported vacuum and when you read vacuum at that port you are no longer getting proper idle mixture adjustments. If you are reading vacuum at that port that means the throttle plates are open to much.
2x500’s equal a lot of CFM, hopefully you have an engine that will digest that amount of air/fuel. I am running two Holley 390’s progressively which is just right for the engine size I have. It still took quite a bit of adjustment and tuning to make them right. I use an air/ fuel gauge to monitor the ratio.
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