I was able to get a bit more info on the problem. The actual mileage is about 170K, not 130K as I originally believed. The engine runs smooth, and the smoke only occurs when engine is revved above idle speeds. The updated head gasket was installed at the same time the valve job on the head was completed. Apparently the 300SD sat unused for about a year until my friend purchased it, and then did a valve job on it. The engine runs fine except for the smoke that only occurs on startup after it has been sitting for a few days. My friend is beginning to think it may be something related to the rings, but it is kind of unusual or problems to occur with the rings at only 170K, and only after the vehicle has been sitting for a few days unused. The problem doesn't manifest itself otherwise.

Thanks for all of the ideas so far.

-Steve

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1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed