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Tips on Tailpipe Reading
Reading tail pipes for fun and profit is not as ridiculous as it sounds -if you know how to read them properly. If your engine is in tip-top operating condition, the coating on the inside of your tail pipe will be dry and light gray in color. This indicates that combustion within the engine is good, -the spark plugs are O.K., and the rings and valves are seating and sealing properly.
If, on the other hand, inspection reveals that the inside coating of the tail pipe is wet, black, and sooty, it indicates that things inside your engine are not so good. Quite likely it means that rings, valves, cylinder walls and even bearings are worn to where they are allowing engine oil to enter the combustion chambers. Some of this oil will "burn off" during combustion, but a good share of it (especially if excessive amounts are present) will be forced out through the exhaust system. Finally, the resultant soot will cling to the inside surfaces of the tail pipe.
According to the engineers at Champion Spark Plug Company, the best time to read your tail pipe is immediately after the car has been given a good run, say ten miles at fairly high and steady speeds. Such a run will give engine performance factors a chance to level off so that you can get a good reading. On the other hand, stop-and-go city driving will probably lead to an erroneous reading because the engine will have been running under generally unfavorable conditions; that is, low engine rpm, prolonged periods of engine idle, etc. As a consequence, tail pipe deposits will reflect an inaccurate reading .
NOTE: If your "Bird" is equipped with a positive crankcase ventilator (PCV) valve, any clogging or malfunction of the valve will often result in a similarly gummed-up tail pipe.
How much engine oil should enter a combustion chamber of a normal engine? Well, as one piston ring manufacturer put it, "If an eight cylinder engine consumed one drop of oil in each cylinder on each stroke at 60 miles per hour, it would use one-and-a-half quarts of oil per mile. However, oil consumption of 1/1 ,500 of a drop per stroke will yield 1 ,000 miles per quart."
Excessive oil in the combustion chambers can be costly in that the oil has to be replaced frequently; but, it can also foul out spark plugs, cause excessive smoking, and generally poor overall engine performance.
The above tip has been passed along by Herb Carrier of the Champion Spark Plug Company.
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