I am looking for help with a rough idling, running 68. The car has had a complete rebuild and, like many others, I have removed the preheated intake air stuff. Before that, it ran reasonably smoothly. I suspect that the missing vacuum advance (in 68) might be the cause. Judging from plug deposits, the mixture seems close and the carbs operate smoothly. The ignition system is all new with an electronic rotor.
Without vacuum advance, it is difficult to get adequate advance at idle without excessive advance at speed. Right now it is set at 15 degrees at 800 rpm and goes well past 30 degrees over about 2500. The centrifugal advance works right on spec.
Does anyone have experience or advice with this? Any help would be appreciated in deciding whether to add a vacuum advance or pursue some other action.