I'm open to ideas on this. Car 1969 Charger: Engine: 426 St. Hemi.
Problem: Car is suffering from a surging irratic idle. Car is all original i.e. carbs, distributor etc...
Car will start immediately just doesn't want to idle. Accelerator pump works and as soon as it is off idle it is fine.
What I've done: Car was in-op for about 2 years. I dropped fuel tank and flushed. Blew out fuel line. Replaced all rubber hoses. Took fuel pump apart and completely cleaned and inspected diaphragm. Cleaned Vapor separator. Rebuilt/cleaned both carbs, Soaked rear carb in cleaner over night to clean internal passages. New needle/seat assay's, set float levels etc.. Pulled distributor and installed new points/condensor, lubed shaft etc...
It is difficult for me to keep the car running long enough to put diagnostic equipment on it ( I work alone).
I've sprayed WD40 around the carbs while it's running to see if there is a vacuum leak and I couldn't detect one.
What am I missing?
Thanks

vac leak. dist weights moving at that idle speed. gummed up carb idle circuit (too lean=not enough fuel to support a stable idle). EDIT not enough initial?

Did you also check the throttle shaft to carb body mating points for leaks. As that point wears you can get erratic idle issues.

Do you run a pcv system on that engine? Try a known good pcv valve to rule out a stuck open valve.

Did you have this issue 2 years ago ?

What is the cam , stock or something with LESS idle vacuum ?

Thanks for the input guys.
To answer the questions:
1. Car has never had any running issues. I've always joked that it's a st. hemi that thinks its a 318.
2. yes, car has a PCV valve. I will check it.
3. Car has stock 1969 mechanical cam. Motor has never been apart.
4. I will check distributor weights. This might be something as I have put a timing light on it and it looks like the timing is way to advanced at low RPM.
5. How do you check the throttle shaft to carb body mating points? Get the car running and try to spray a liquid just on those points?

spray the shaft on both sides & make sure the vapors dont go up along the carb sides & get sucked in the air horn & give you a false reading (piece of cardboard or paper)

If it has PB, the hose or booster could have a pretty good vacuum leak. Maybe just pull the hose and cap the vacuum nipple as diagnostic. Same for the PCV line.

I guess a sneaky vacuum leak or gummed up idle circuit.