Classic/Antique Car Repair: rings or valves, manifold vacuum, piston rings

Question
Brad, My 55 Chevy, 235ci 6 cyl, powerglide is starting to smoke a little blue smoke. Mostly at a light while at idle coming from the crankcase draft tube, or it's noticeable it in my mirror coming off the freeway coasting down from speed. Car runs great other than that. Would this be caused by piston rings or by valve guides?

Answer
At this point without a compression test my guess is that it is mostly Valve guides and or seals. That is indicated by the smoke under deceleration when intake manifold vacuum is the highest. Some times an examination of the spark plugs will give a clue. If the oil splatter, dark spots on the tip insulator, are on one side then that indicates valve guides. As that surface was closest to the valves and received the full spray of oil. The smoke coming from the breather tube is more of an indication of compression rings slightly leaking blow by into the crankcase. Two different problems.
Brad