I fully agree with Jerry. There is no reason to use non-detergent oil in a stovebolt engine. It's just not a very good automotive engine oil. There is a reason engines used to require a rebuild every 50,000 miles or so: the oil did not carry the gunk out when you changed it, so the engines got plugged up and the new oil was quickly contaminated.
Run the best oil you can afford no matter what the service history of the engine. But if you are switching from non-detergent to detergent, DO take off all the covers and clean everything up including the oil pickup screen. This way you can pro-actively replace all the gaskets that will start leaking as the detergent oil starts to clean the gunk out that has been sealing up the covers.
And Jerry is right on about the size of particles held in suspension by detergent oil. They don't get filtered out. When you see that your oil is black after running a bit, this does not mean the oil is shot, it means the oil is doing its job, picking up fine particles. The oil is designed to continue to lubricate while doing this.
Kurt
