I have a 1948 DeSoto Custom four door sedan with the M-6 hydraulic transmission and the engine smokes excessively nearly all the time. The engine sounds good with no knocking sounds and it idles perfectly. The smoking is greater while taking off from a complete stop after the car has been idling for a while. I have tried Lucas oil supplement and it is not helpful. The car sat for many years until I got it in 1997 and the restoration has been a slow process, so it has also sat a lot since I have owned it. Some of the local old car collectors have told me that the problem is likely that the lower set of piston rings have corroded from the long time of inactivity which does not damage the upper rings as badly. This is why the engine runs and sounds fine and passes a compression test. Others have told me that it is likely that the valve guides are allowing oil to get where it does not belong. Others have told me that this is less likely the problem since defective valve guides smoke the worst when the car is first started and then the smoking decreases. This is not the scenario with my DeSoto since it smokes all of the time.
I would appreciate any opinions or advice on this smoking situation with my DeSoto. I noticed when I registed to post on the website that DeSoto is not listed among the choices of makes of cars. DeSoto was made by Chrysler from 1928 to 1961 and was comparable in cost to a Buick or Oldsmobile of those years. Many taxi companies used DeSotos during the 1940s and early 1950s because the M-6 transmission, which was coupled with a Fluid Drive unit made the cars much easier to drive in city traffic. Thanks for your help