Very unlikely to have a base idle setting, the idle speed control valve does all of this, there will be a tiny screw that the throttle linkage on the tb rests on at idle, this is NOT to set the base idle, but to ensure the flap in the tb doesn't stick shut it holds it very slightly open, but not enough air to run the engine.
I assume you are having idle probs ?.
I assume this is not a cossie DOHC ?
tabetha