Per,

 

If there is any oil remaining in a cylinder after shutdown it will migrate to the lowest point.  Sometimes the lowest point location is at the lower plug, but not always.  The oil's final resting place may depend on the orientation of the engine in its mount and the angle of the aircraft in its usual parking spot.  Cylinder one just might collect residual oil at the spark plug while other cylinders do not.

 

New cylinders that are not yet broken in generally allow more oil to pass into the cylinder than those that have 40 or so hours run at high power. This does not completely answer the question about the source of the oil.  Some oil can certainly get by the piston rings or through valve guides.  Even if one gets 10 hours per quart, the oil consumed is either being thrown overboard or is entering the cylinders and being burned along with the fuel.

 

When the motor is running, any residual oil should be completely burned if the combustion event is correct.  If the air/fuel ration is correct because it matches the other cylinders, the only other source of incomplete combustion is the ignition component.  Either the timing is off, or there is a fault in the magneto, harness or plug.  However, you have checked these components.

 

In flight temperatures (CHT and EGT) may provide a clue.  Perhaps the GAMI lean test could provide more information about the performance of cyl 1 versus the others. 

 

Scott Krueger

Lancair 320 Lyc IO320

 

 

After flying 200 hrs with my IO 320, I got continuous oil in lower first cylinder spark pluck.

Install new cylinder and piston, new fuel injector, leak-checked the pipes in the oil pan……check pluck, magneto and harness.

Flown the airplane 10 hrs now on 75% + but still have the problem. Any idée?

 

Per

OY-JCP

LNC 2