Remember when you could set points with a feeler gauge and a timing light?
I used to carry a dwell meter and a timing light in my truck every day back in the 80s. Now I just plug in the scanner and watch the live data on a screen. Does anyone else miss the hands-on feel of setting an engine by ear and touch?
Actually, a happy engine should sound smooth and even, not really like a purr. That purring noise you hear is often the fan belt or maybe a bearing starting to go. Might be worth getting that checked out.