A 65 Continental

E

Edgefly

Pre-takeoff checklist
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Edgefly
My A 65 Continental has a suspicious little report from its' last annual. It has only 238 hours SMOH when all 4 cylinders were replaced with Mileniums. It has had good compression readings (>74/80 since the MOH 8 yrs. ago)until this last annual when #2 dropped from 74/80 to 64/80. The other three were 72-76/80 and all had been >74/80. Now, I realize that this is not exactly crisis status but am wondering uif I should have some checks made to look for likely upcoming problems. The engine seems to run fine and and there is negligible oil usage so no other change has been noted.

Dale
 
Edgefly said:
My A 65 Continental has a suspicious little report from its' last annual. It has only 238 hours SMOH when all 4 cylinders were replaced with Mileniums. It has had good compression readings (>74/80 since the MOH 8 yrs. ago)until this last annual when #2 dropped from 74/80 to 64/80. The other three were 72-76/80 and all had been >74/80. Now, I realize that this is not exactly crisis status but am wondering uif I should have some checks made to look for likely upcoming problems. The engine seems to run fine and and there is negligible oil usage so no other change has been noted.

Dale
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do the plugs look different than the others?
 
Can you hear if it's leaking out the exhaust or breather? I'm not sure how obvious it'd be since that's not a huge leak. For starters I wouldn't do a thing without flying it some and checking again

How was the check performed? Per the cont sb? It could always be human error as well.

If it were mine I would fly for a few hours then check again with me either doing it or watching it done to make sure no errors were being made.

All that said not sure I would replace at those values anyhow...all depends.
 
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The exhaust valves are famous for leaking. An engine that sits gets some corrosion on the valve and seat and can leak. Fly it and then test it again, but this time listen at the oil cap and exhaust pipe to see where it's coming from.

Those little engines also have hydraulic valve lifters that will sludge up with infrequent use and short flights, and they get sticky. A sticking lifter can hold the valve off its seat once the engine has cooled down, and it will show poor compression.

Dan
 
Was the same EXACT gauge and orifice used this time? Calibration of them is something that doesn't happen often, one or the other(prev or current) could be well out of spec.
 
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docmirror said:
Was the same EXACT gauge and orifice used this time? Calibration of them is something that doesn't happen often, one or the other could be well out of spec.
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If it is the gauge wouldn't all the cylinders be effected?
 
Tom-D said:
If it is the gauge wouldn't all the cylinders be effected?
Click to expand...

Yes, but the others came down a bit too. Not as dramatic, but different. Also could be an issue with #2 including a calibration change.
 
The numbers are only half the story. Where is it leaking? That is the whole point of doing a differential/leak down test to begin with. Most of the trouble with these small Continentals is due to lead, they just don't develop the heat and pressure needed to adequately deal with the high levels in 100LL. You might try running some TCP or other scavenger product containing EDB and see if it helps any. I wouldn't get too worked up over the numbers you're seeing, at least not from just a single test result. Find out where the leakage is and keep an eye on it.

And do more flying, that always helps :yes:
 
Plenty of the little engines don't have a mixture control, and rely on altitude changes to make mixture changes. Problem is, a carb is still a carb and although in knows something about lower differential pressure, it's still set to provide a fixed mixture based on throttle(with some exceptions for emulsion). So, flying at higher altitudes in the non-mixture engines makes for too rich running, and carbon/lead buildup.
 
docmirror said:
Plenty of the little engines don't have a mixture control, and rely on altitude changes to make mixture changes. Problem is, a carb is still a carb and although in knows something about lower differential pressure, it's still set to provide a fixed mixture based on throttle(with some exceptions for emulsion). So, flying at higher altitudes in the non-mixture engines makes for too rich running, and carbon/lead buildup.
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why wouldn't it effect all cylinders equally? why just the 1 that is lower than the others?
Reading the plugs you can tell if the one is running richer/ leaner than the others and go from there.
 
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