I did an oil change in my old 292 and ran a quart of ATF. Cleared carbon within minutes. I had a valve sticking and I left the engine at about 1500 rpm....poured a quart of ATF in and misfiring stopped a few minutes later. Ran it for about 20 miles...drain and changed the oil. Never smoked At All which was surprising for an engine with 150,000 and 95 pounds of compression vs at least 130. Could be weak rings for sure....Engine Restorer seems to help as well. I used a can of that and it bumped my compression up to about 115 pounds in all cylinders...hence the conclusion...Weak Rings.
