Strange engine event

I've never heard of piston rings rotating. Kind of makes staggering the

I had a Chevy pickup years ago that I changed the rings on one cylinder twice.
(This was before I had enough money to do things right) All five grooves on the
piston rings would be in a vertical row letting the oil get by and smoke. The
machinest said that the one cylinder was way out of round and the rest were OK.
He said that the rings rotated on the pistons so I believed him. Before that I
wondered why a good mechanic cleaned the grooves and rotated the rings before
He installed them.

Now for the other side. I overhauled a 225 HP Johnson outboard (Never again,
Too many pieces) The piston rings have keepers on them to keep them from
rotating. The oil injection must keep them from scoring.

The terminology Stuck Ring. I wonder if that means Rotation or Stuck in the
ring land or groove?

Like I say I am an amateur and the only way that I have learned is by doing it
myself because I didn't have enough money to let someone else do it.

Could a lifter have stuck open or closed? Had one stick on a 172 and knocked a
hole in the rocker cover.

It's a fouled plug, burned valve or broken ring.

Fouled plug, maybe as it could clean itself up, a burned valve or broken ring
wouldn't fix themselves.

It's a fouled plug, burned valve or broken ring.

Fouled plug, maybe as it could clean itself up, a burned valve or broken ring
wouldn't fix themselves.

I certainly doubt something like a broken ring as well since the
problem has not yet re-appeared.

As far as the fouled plug theory - could a plug really get fouled
that quickly? Remember the plot looked like a sharp step function.
Most of the EGT/CHT change occurred in the first 20 seconds of the event.

So for now I think the injector theory, or the stuck valve or lifter
theory is more likely.

By the way I flew again yesterday for 2.5 hours and the problem
still has not repeated. So it may be awhile (if ever) before we
figure out the real cause.

~Paul

Hi Paul

The original reply that I gave you was for one cylinder.
Rereading your post, it seems that the readout was for all cylinders,
which changes the cause to Timing out or bad magneto.
(And no, I'm no expert on this stuff - I'm giving you these answers
right out of the book for my own engine analyzer).

HTH

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument
Cessna 172H C-GICE


In article nospam-1C6AA9.22284826062004@shawnews,
tony roberts wrote:

It's a fouled plug, burned valve or broken ring.
And that is straight fom the book on my engine analyzer

Tony
C-GICE


In article ,
"Paul Mennen" wrote:

For the last 200 hours I've recorded all the data from my engine
analyzer which makes it easy to look at such things. Anyway a week
ago I was flying along steady at 12 thousand feet when I noticed
an unusual shift in the engine bar graph display. Looking at the
recorded data I see that all flight data is rock steady and all
engine data (and fuel flow) is also rock steady except for EGT1
and CHT1. From the beginning of the event this is what it looked
like:

Time after event EGT1 CHT1
---------------- --------- ---------
t = 0 1355F 300F
t + 20 seconds 77F rise 7F drop
t + 80 seconds 100F rise 19F drop
t + 3 minutes 114F rise 25F drop

After that it was pretty much steady, but I reduced power after
a few more minutes. (By the way, this is a Turbonormalized IO550.)
So EGT1 which was the coolest (as usual), rose to the level of the
warmest few cylinders. And CHT1 was the coolest (as usual) and
dropped away even more below the average. Still the final temps do
not seem that alarming, but when you look at the graph it looks
really strange since I've never seen such step changes unless it
was in response to some control input.

In the few flights I have taken since that event, I haven't seen
anything unusual like this happen again.

So to those of you who understand internal combustion engines -
what can cause a sudden drop in power in one cylinder like this?
Could something have fallen into this cylinder or could a
valve stick for a while or something? Or is this a sign that
something is breaking? What would you do about it? -
- Keep a close eye on it?
- Do an oil analysis?
- Ground it?
- Have a mechanic look at it?

Can a bad mag or spark plug cause such a thing? (BTW the engine
is a factory remain with 300 hours on it).

Thanks in advance for any insights you may have.
~Paul

I thought the values were only for cylinder #1 - hence the EGT1 and CHT1
headings.

--
Jim Carter
"tony roberts" wrote in message
news:nospam-978501.00081830062004@shawnews...
Hi Paul

The original reply that I gave you was for one cylinder.
Rereading your post, it seems that the readout was for all cylinders,
which changes the cause to Timing out or bad magneto.
(And no, I'm no expert on this stuff - I'm giving you these answers
right out of the book for my own engine analyzer).

HTH

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument
Cessna 172H C-GICE


In article nospam-1C6AA9.22284826062004@shawnews,
tony roberts wrote:

It's a fouled plug, burned valve or broken ring.
And that is straight fom the book on my engine analyzer

Tony
C-GICE


In article ,
"Paul Mennen" wrote:

For the last 200 hours I've recorded all the data from my engine
analyzer which makes it easy to look at such things. Anyway a week
ago I was flying along steady at 12 thousand feet when I noticed
an unusual shift in the engine bar graph display. Looking at the
recorded data I see that all flight data is rock steady and all
engine data (and fuel flow) is also rock steady except for EGT1
and CHT1. From the beginning of the event this is what it looked
like:

Time after event EGT1 CHT1
---------------- --------- ---------
t = 0 1355F 300F
t + 20 seconds 77F rise 7F drop
t + 80 seconds 100F rise 19F drop
t + 3 minutes 114F rise 25F drop

After that it was pretty much steady, but I reduced power after
a few more minutes. (By the way, this is a Turbonormalized IO550.)
So EGT1 which was the coolest (as usual), rose to the level of the
warmest few cylinders. And CHT1 was the coolest (as usual) and
dropped away even more below the average. Still the final temps do
not seem that alarming, but when you look at the graph it looks
really strange since I've never seen such step changes unless it
was in response to some control input.

In the few flights I have taken since that event, I haven't seen
anything unusual like this happen again.

So to those of you who understand internal combustion engines -
what can cause a sudden drop in power in one cylinder like this?
Could something have fallen into this cylinder or could a
valve stick for a while or something? Or is this a sign that
something is breaking? What would you do about it? -
- Keep a close eye on it?
- Do an oil analysis?
- Ground it?
- Have a mechanic look at it?

Can a bad mag or spark plug cause such a thing? (BTW the engine
is a factory remain with 300 hours on it).

Thanks in advance for any insights you may have.
~Paul

(PInc972390) wrote in message ...
I've never heard of piston rings rotating. Kind of makes staggering the

I had a Chevy pickup years ago that I changed the rings on one cylinder twice.
(This was before I had enough money to do things right) All five grooves on the
piston rings would be in a vertical row letting the oil get by and smoke. The
machinest said that the one cylinder was way out of round and the rest were OK.
He said that the rings rotated on the pistons so I believed him. Before that I
wondered why a good mechanic cleaned the grooves and rotated the rings before
He installed them.

Rings aren't supposed to rotate. No cylinder is perfectly round, and
we crosshatch cyinder walls and use mineral oil for a few hours so
they'll wear the rings and the rings will wear the cylinders until the
ring's outer circumference matches the imperfect cylinder bore. If the
rings rotate they'll spoil that match. If you find them rotating, then
the bore is probably badly out-of-round and the ring ends are seeking
the apex of the wider diameter; the pointy end of the egg, if you
will. Properly overhauled engines have been cylinder bored to get them
round before honing, or they've been honed on a rigid hone such as the
Sunnen CK-10 or CV-616, an expensive piece of machinery that I never
want to operate again. I wish I had as many flying hours as honing
hours.
The cylinder can be honed to a really close roundness, but
bolting it to the case distorts it somewhat anyway. As I said, no
cyinder is perfectly round.


The terminology Stuck Ring. I wonder if that means Rotation or Stuck in the
ring land or groove?

Stuck in the groove, usually by a buildup of carbon and crud
behind and around the ring. The piston will hold onto the ring instead
of letting it follow the cylinder wall, and a bad seal results. When
the crud gets hot it will sometimes let go, but seize the ring again
when cold. Poor compression and some smoke while warming up.



Like I say I am an amateur and the only way that I have learned is by doing it
myself because I didn't have enough money to let someone else do it.

Some of us are glad for the company. Maybe most of us.


Dan

On re-reading it, you are correct.
Oh well - I already answered that one

Tony



I thought the values were only for cylinder #1 - hence the EGT1 and CHT1
headings.

--
Jim Carter
"tony roberts" wrote in message
news:nospam-978501.00081830062004@shawnews...
Hi Paul

The original reply that I gave you was for one cylinder.
Rereading your post, it seems that the readout was for all cylinders,
which changes the cause to Timing out or bad magneto.
(And no, I'm no expert on this stuff - I'm giving you these answers
right out of the book for my own engine analyzer).

HTH

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument
Cessna 172H C-GICE


In article nospam-1C6AA9.22284826062004@shawnews,
tony roberts wrote:

It's a fouled plug, burned valve or broken ring.
And that is straight fom the book on my engine analyzer

Tony
C-GICE


In article ,
"Paul Mennen" wrote:

For the last 200 hours I've recorded all the data from my engine
analyzer which makes it easy to look at such things. Anyway a week
ago I was flying along steady at 12 thousand feet when I noticed
an unusual shift in the engine bar graph display. Looking at the
recorded data I see that all flight data is rock steady and all
engine data (and fuel flow) is also rock steady except for EGT1
and CHT1. From the beginning of the event this is what it looked
like:

Time after event EGT1 CHT1
---------------- --------- ---------
t = 0 1355F 300F
t + 20 seconds 77F rise 7F drop
t + 80 seconds 100F rise 19F drop
t + 3 minutes 114F rise 25F drop

After that it was pretty much steady, but I reduced power after
a few more minutes. (By the way, this is a Turbonormalized IO550.)
So EGT1 which was the coolest (as usual), rose to the level of the
warmest few cylinders. And CHT1 was the coolest (as usual) and
dropped away even more below the average. Still the final temps do
not seem that alarming, but when you look at the graph it looks
really strange since I've never seen such step changes unless it
was in response to some control input.

In the few flights I have taken since that event, I haven't seen
anything unusual like this happen again.

So to those of you who understand internal combustion engines -
what can cause a sudden drop in power in one cylinder like this?
Could something have fallen into this cylinder or could a
valve stick for a while or something? Or is this a sign that
something is breaking? What would you do about it? -
- Keep a close eye on it?
- Do an oil analysis?
- Ground it?
- Have a mechanic look at it?

Can a bad mag or spark plug cause such a thing? (BTW the engine
is a factory remain with 300 hours on it).

Thanks in advance for any insights you may have.
~Paul







--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument
Cessna 172H C-GICE

"Jim Carter" writes:


What causes the piston rings to rotate? Since the piston movement is
perpendicular to the cylinder wall, there must be some other mechanism other
than just piston movement causing them to rotate.

Very Clever Design. I can't recall the details, but ISTM there are
[automotive] patents on making 'em creep along.

Also, why would the grooves on the rings have to be lined up to allow
leakage through the groove?

It does leak lots more; the gap between the rings is not all that
far, I guess...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

perpendicular to the cylinder wall, there must be some other mechanism other
than just piston movement causing them to rotate.


I just can't get it into my head how that a ring can be put in and when the
engine is torn down all of the grooves will be in the same place as when
installed.

The keepers on a two cycle boat engine (not motor) are the only anti - Rotation
device that I have seen.

Dave,
I've torn engines down before and the distance between the rings is
relatively a lot more than the gap between the ends of the ring when
compressed into the cylinder. It is such a big difference that I don't see
how the intra-ring distance could be restrictive to the flow of gasses
passing through the ring gap.

I'd really like to see some information on the "Very Clever Design" you
mentioned. Even if the cylinders were honed with a diagonal pattern,
shouldn't the ring just reverse direction at the end of the stroke and
follow the honing marks?

--
Jim Carter
"David Lesher" wrote in message
...
"Jim Carter" writes:


What causes the piston rings to rotate? Since the piston movement is
perpendicular to the cylinder wall, there must be some other mechanism
other
than just piston movement causing them to rotate.

Very Clever Design. I can't recall the details, but ISTM there are
[automotive] patents on making 'em creep along.

Also, why would the grooves on the rings have to be lined up to allow
leakage through the groove?

It does leak lots more; the gap between the rings is not all that
far, I guess...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433