Idle up and down

[TF360]

1974 Duster 360 4-speed. Trying to get a few opinions on this problem. Car runs pretty good , but when I come to a stop after its warm the idle will stay high and then drop down to a slow idle. The throttle is returning properly-return spring working properly. Eddy 600cfm. Carb fairly new but same issue with old carb. Is this a symptom of something common. Also just did a tune up-plugs wires cap rotor ect.

 

[mderoy340]

check mechanical and vacuum advance is operating smoothly. Slow return on timing could cause your issue.

 

[TF360]

Thanks mderoy340.

 

[TrailBeast]

check mechanical and vacuum advance is operating smoothly. Slow return on timing could cause your issue.

X2, and idle RPM can be an issue there also.
Try setting the RPM lower if you can because the advance weights might be advancing at idle.

(Just as a diagnosis so you know whats going on.)

 

[TF360]

Thanks Trail

 

[RedFish]

Faults in fuel delivery will do that too. Fuel boiling in the bowl, filter, and line.
If it runs perfect from cold start. Idle rpm cycling up and down only after warmed up...

 

[AJ/FormS]

Sticking flyweights in dist. or Carb speedscrew in too far causing transfers to flow, or float level too high, or any combo. Make sure the advance is not too retarded.