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O-360 detonation issues

Tom3holer

MEMBER
Cape Cod
Hi,
I tried to find an appropriate section on the forum here to ask this question. I hope this might be the place.

A good friend of mine has a O-360 powered C-170. He and his AI found a high time engine and bought it. The AI did a major overhaul including new pistons.
The owner wanted a new electronic ignition installed on one side during the rebuild. A Shurefly was installed. It was set to run as a normal mag with no timing change for some 30 hours and all was fine. He then decided to move the dipswitch to activate the advanced timing with the help of another mechanic that was not familiar with the Shurefly. Apparently, he set the timing to the normal 27 deg btdc. The owner asked me to fly with him after some 10-15 hours as it was running rather rough. I did and agreed it was running rough so we cut the flight short. At that point I didn't realize he had changed the E I settings. Fortunately he had done an oil check shortly before and indeed there was metal in the oil. The AI grounded it and discovered what looked like severe detonation had/was occurring. The rod bearings looked like a high time engine and he showed me the pistons and they looked like somebody has sandblasted the skirts on all 4. The cylinders inside had a mirror finish with no signs of crosshatch anywhere. He then discovered the timing on the EI mag was supposed to be set at 0 deg not 27 btdc when the unit is running variable timing. So basically it was running at 54 deg btdc. The rods are being sent out for inspection and new bushings and bearings and he ordered new pistons.
The issue we discussed is whether the case should be split to look at the crank bearings. The AI was of the mindset that as the rod bearings look like high time bearings but no abnormal signs the crank bearings should be in good condition.

What do you Gents with many engine overhauls under your belt think?
 
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Not a big time overhauler but once you get metal in the oil you don't know how much got imbedded in the crank bearings. I would split the case. So what was the CHT'S while all of this was happening?
DENNY
 
Owner ran it rough and never tried switching mags? Edit: During a runup or while flying?


Gary
 
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Pretty confident that the surefly mags are always supposed to be set to TDC on #1. A selection is made with switches to let it know how much to advance and if you want dynamic timing. It was probably waaaay advance even before, then became so advance with dynamic timing that it was having trouble. Did it have an oil filter or screen? Probably worth a call to lycon or aerosport to see what the real experts think.
 
I don't know the whole story. The AI told me he ran it for some 10-15 hours with the incorrect setting on the EI.
The owner initially thought it was the new prop as he put on; a new MT prop on it about the same time. Thats what I thought also when I flew with him. The owner has a nice engine monitor package, however from the right seat I can't see it so don't know what the head temps were.
Tom
 
Thank you all for the suggestions and thoughts.
Yes it has an oil filter, and I suggested he call lycon which I believe he is doing tomorrow.
 
Just pull it apart- the only extra parts cost will be a few gaskets and main bearings- cheap in the scheme of things. Easy to do at this point instead of having questions in the back of your mind for the next 2k hours…. I would think some of the labor is on the IA if he installed the surefly? If I had built that engine and installed the ignition, I’d want to have a look for my own peace of mind.. I gotta think there were red flags prior- I didn’t know these things would even run, much less well at 54btc- but then I’ve never tried…
 
Reading is important. From the OP's #1:

"The owner wanted a new electronic ignition installed on one side during the rebuild. A Shurefly was installed. It was set to run as a normal mag with no timing change for some 30 hours and all was fine. He then decided to move the dipswitch to activate the advanced timing with the help of another mechanic that was not familiar with the Shurefly. Apparently, he set the timing to the normal 27 deg btdc. The owner asked me to fly with him after some 10-15 hours as it was running rather rough."

Reads to me like the owner created the problem, then continued to fly despite the apparent change in conditions. Bet the owner never has had a valve stick, or carb ice over open water or rough terrain.

Hope it's fixed.

Gary
 
at this point finger pointing is too late. If I were doing the job I would treat it as a catastrophic failure. That means tear it down to the last nut and bolt. Then inspect and clean everything. Get the book and overhaul the engine. All you need is a chunk of steel stuck in an oil passage to get in the main bearings ,etc., So the thought of not opening the cases for cleaning at a min. Makes me shake my head. I’m sure I don’t know everything about this but from what you said I would insist on an overhaul. I am a IA and do overhaul engines and this is where I stand. Sorry to be A wet blanket but I want to sleep at night.
 
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