Classic/Antique Car Repair: Blue smoke on acceleration, Engine Oil usage diagnosis

Question
Hi Robert-

I have a 1959 Chevy with the 235 6 cylinder and 3 speed manual transmission. When the engine is under a heavy load (like accelerating quickly from a stop or going up a steep hill)blue smoke comes from the tail pipe. It can idle and cruise at a steady speed with no smoke and uses only a little oil, maybe a quart low by the end of the summer if I drive it a lot.

An "old timer" told me you can tell if it is bad rings or bad valves by when it smokes but he doesn't remember which is which. Bad valves he said thicker oil or STP will help, but bad rings he said there is nothing short of an engine overhaul to help. Any idea if it is bad valves or bad rings, and if bad rings anything to help until an engine rebuild which would be in the considerable future?

Thanks,
Jim

Answer
Hello Jim,

A bat wing '59 Chevy, certainly a car worth preserving!

Your mechanic is giving you valid information, as far as it goes. Oil smoke on acceleration is symtomatic of rings or similar and smoke on deceleration is generally oil seals or similar. To be sure of each (or both), have your mechanic do a Cylinder Leakdown Test. This involves removing the spark plug on the Number 1 cylinder, placing  the cylinder at Top Dead Center (TDC)so both valves are closed and piston is at the top of it's compression stroke, install an air line adaptor in the spark plug hole and then applying compressed air. If your hear air leakage through the carb, it's valves/valve seals. However, if you hear air leakage through the dip stick tube, it's rings. If it's both, which I suspect you may have given the well used sound of your engine, sorry but it's rebuild or major overhaul time.

Given a rings diagnosis, the only short term thing you can do is thicken the oil through either a heavier viscosity oil (I'd recommend 20W50) or an oil thickener like STP. If it's valve seals, there is a way to replace them without taking the head off. There are special tools that can compress the valve spring and allow seal replacement without allowing the valves to fall into the cylinder when you do it. Again, you're mechanic should be able to do this also. If he/she can't, it's red flag about his mechanic qualifications so you need to engage with someone that is comfortable diagnosing and fixing this type of problem.

Best of luck keeping this unusual car on the road!

Bob