You may want to pull the valve cover first and inspect the area where the pushrods pass through. It is a common fail point when a hole will develop and allow oil to drop directly into the exhaust manifold passage of the head, bypassing the cylinder, which would explain why you don't have significant smoke.. There would also be evidence of the hole by examining the smoke coming from the oil fill hole while running. It is often confused with piston ring wear but piston ring wear doesn't allow for the passage of oil to the exhaust. My suggestion is to examine the yoke between the passages and if nothing is found, remove the head and have it checked at a. machine shop if nothing leaps out at you. Oil dropping onto the dry side of a mixing elbow will produce white smoke at the exhaust temperature rises but will pool oil in the exhaust when it is cooler, like after initial start up and after shut down. It doesn't hurt to look.