I have a '55 322 nailhead that is purring beautifully. Problem is that it's been sitting for a few years before I acquired it recently. I've changed the oil with a bottle of Marvel Mystery Oil and had it running off and on for quite a bit. It has good oil flow, lifters and rods doing their job, etc. On startup no heavy blue smoke out the tailpipes on idle, little bit when hitting the throttle. However, once it warms up that all changes to heavy blue and I start seeing a bit of blue smoke coming out of the valve cover vents as well. Before I start the tear down, do you think it sounds more like worn valve guides, oil rings, or both? :confused: