GMC Repair: Exaust Smoke, valve stem seals, combustion chambers

Question
Dear Sir:

I have a 1992 GMC Conversion Van, 350, 5.7 litre, V8, 3/4 ton, G2500 series.  When I start my engine, there is a big ball of blue smoke coming from my exaust pipes.  Then it becomes a light grey steady stream of smoke when the engine is idleing or driving.
Sometimes it will stop, and then it starts back smoking again.
What is causing this?
Your advice will be greatly appreciated.

Mr. Thomas

Answer
Blue smoke is oil being burned in the combustion chambers. Most likely due to:

1. Weak and worn valve stem seals.
2. Weak, worn or cracked piston oil rings.

IF you are NOT experiencing a major loss of fuel mileage, I would have to say that the GRAY smoke is also most likely a combination of oil and gas being burned in the combustion chambers.

I do NOT see any immediate concern at this time, But if the smoke becomes ALWAYS evident at ALL times this would require repair.


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