Stuck Valve

timwinters said:
I agree completely but, when it only sticks for 15 seconds and then unsticks, it's impossible to tell which valve is the issue.
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It's also impossible to tell if...

1) More than one valve is sticking, and...

2) Exactly when and where and under what conditions the valve is going to seize tight in its guide, causing a huge loss of power, combined with lots of vibration and possibly major engine damage.

If #2 happens on takeoff, let's say, it could lead to fatal consequence.

I think you're taking this way too cavalierly, but it's your life.
 
timwinters said:
Oh, it's a sticking valve.

My first suspect is the auto gas I burn (typical blend is 75% MoGas, 25% 100LL) We had to overhaul one cylinder a couple of years ago due to a worn valve guide, leaky valve, as you describe and I was amazed at the amount of auto gas varnish that was built up on all the various components. That can't be good for keeping valves unstuck.
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How many times in the past on this page and others have I said that auto fuel is not an end all to engine problems? It's just a different set of problems. This is one of them.

Which requires me to ask, what is the only good thing that a leaded fuel does for us that a unleaded fuel can't?
 
Originally Posted by timwinters
I agree completely but, when it only sticks for 15 seconds and then unsticks, it's impossible to tell which valve is the issue.
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Too bad you don't have an engine analyzer, that would tell you which cylinder it is at least.
 
We all know that most accidents are the results of more than one "link". That removing even one link may likely have prevented the accident entirely.

Tim currently has one link already in place - operating with a known deficiency.

And, God forbid, that would likely be listed as a contributing cause were something bad to happen.

Just sayin'.
 
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Tom-D said:
Maybe, maybe not.



It does run normally most days.
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A stuck valve? Yea, it would tell you what cylinder. I had a fouled plug and I could tell which plug it was by switching magnetos. You would be able to download the data and analyzed in detail if you couldn't figure out what was happening at the time.
They are a must have IMHO.
 
Why would an engine with <150 hours do this? ('Cause I've seen it happen).


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Henning said:
Too bad you don't have an engine analyzer, that would tell you which cylinder it is at least.
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I do...but it unstuck before I even had a chance to turn the avionics master on, much less the monitor "boot up" which takes another 10 seconds or so...
 
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timwinters said:
I do...but it unstuck before I even had a chance to turn the avionics master on, much less the monitor "boot up" which takes another 10 seconds or so...
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Might want to start turning it on beforehand and turning everything else off by its own switch for the startup until you catch it.
 
Henning said:
Might want to start turning it on beforehand and turning everything else off by its own switch for the startup until you catch it.
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Still don't know how that would help. Both EGT's and CHT's are nil for the first "few moments" after start up on my EI UBG16.

But I'm all ears!

(Mine is the older "non-recording" type).
 
timwinters said:
Still don't know how that would help. Both EGT's and CHT's are nil for the first "few moments" after start up on my EI UBG16.

But I'm all ears!

(Mine is the older "non-recording" type).
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If the thing is up, you may see one EGT come up last.
 
timwinters said:
I do...but it unstuck before I even had a chance to turn the avionics master on, much less the monitor "boot up" which takes another 10 seconds or so...
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Mine is wired to the main bus for just that reason... but it still wouldn't really help to diagnose it if the roughness went away after 15 seconds. It takes that long for the unit to complete its self test and advance past the "splash" screen.
 
azure said:
Mine is wired to the main bus for just that reason... but it still wouldn't really help to diagnose it if the roughness went away after 15 seconds. It takes that long for the unit to complete its self test and advance past the "splash" screen.
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Wire it to a separate small battery for a while (fire alarm system batteries are good for this) so you can have the unit up and running on start up.
 
I'm sorry I don't know a perfect answer for the OP, but for some who wonder why it happens I may have an insight to one piece of the problem. The O-470 engine has a cylinder volume of 78 CuIn, the O-200 has a cyl volume of 50 CuIn. Although the valves for the O-470 are in fact larger, if you take the exhaust pipe off of a O-200 it will fit perfectly on the barrel of the O-470. That to me says there is a restriction in the exhaust path on the O-470 where I think the exhaust port, and manifold plate should be about 30% larger.

This is one mans opinion, and you are welcome to ignore it. But first - go get a O-200 exhaust pipe and fit it to an O-470 jug and see for yourself. Hmmmmmm

YMMV, don't try this at home, pro driver closed course, objects in mirror, and may cause anal leakage.
 
timwinters said:
But I'm all ears!
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Then do as I told ya, hand prop it every morning until you fine the cylinder that has no compression.

Or junk the chrome cylinders and get new cerminll cylinders.
 
Well, I flew it for an hour yesterday to warm the oil and then changed it. I do believe i found the answer. Attached...

Now it's a matter of determining which one.
 

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Henning said:
Wire it to a separate small battery for a while (fire alarm system batteries are good for this) so you can have the unit up and running on start up.
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Why not just pull CBs for sensitive equipment and power up, wait for the boot process to complete, start engine.
BTW, do we really need to be worried about voltage spikes anymore with modern equipment?
Most modern equipment is dual voltage and has voltage regulators built in.



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Tim....just so you know, your images don't display on my PC. :D

showthread.php
 
Pull the cylinder .....fix it correctly....save a lot of grief and possibly avoid a terrible situation!!!
 
cdahl said:
Pull the cylinder .....fix it correctly....save a lot of grief and possibly avoid a terrible situation!!!
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Yeah, that's the game plan now that I discovered some bronze in the filter...but determining which cylinder it is might be the interesting part if the compression test doesn't make it obvious.
 
Checkout_my_Six said:
Tim....just so you know, your images don't display on my PC. :D
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Hmmm...I just fired mine up and it displayed. Regardless, here it is again with an additional shot.
 

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Not to be too skeptical but wouldn't bits of the inner end of the valve guide go out through the exhaust? It's in the upper cyl air path. Unless there is a fracture in the outer end of the guide, which seems far far less likely. Check for what other components on the inside of the engine are brass/bronze. If it is the outer lip of the guide that things pretty wobbly.
 
You've got 15 hours flight time on that timebomb now. Please inform your passengers before they go up with you if you decide to fly it again like that, and avoid populated areas.
 
PaulS said:
You've got 15 hours flight time on that timebomb now. Please inform your passengers before they go up with you if you decide to fly it again like that, and avoid populated areas.
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No passengers in that 15 hours...unless you count two german shepherds and a bulldog! ;)

And, yes, once metal is found in a filter, there will be no more recreational flying until the source is found and corrected...that's why I changed the oil yesterday. To see.

The only place it's getting flown to now is to my mechanic...about 30 minutes.

If, OTOH, you're referring to the 15 seconds of stuck valve and not the filter photos when you refer to it as a "timebomb" then, no, I don't have 15 hours on it. I have over 700. :yikes:

Thanks for you concern.
 
docmirror said:
Not to be too skeptical but wouldn't bits of the inner end of the valve guide go out through the exhaust?
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Good point. The only other thing I've found thus far that's bronze/brass is the starter adapter. I'm having a hard time finding a all inclusive diagnostic chart that lists different metals and possible sources. If someone has one, I'd love to see it!

Put a call into my mechanic today. He hasn't gotten back with me yet. Hopefully it'll be in his hands NLT tomorrow.
 
timwinters said:
Good point. The only other thing I've found thus far that's bronze/brass is the starter adapter. I'm having a hard time finding a all inclusive diagnostic chart that lists different metals and possible sources. If someone has one, I'd love to see it!

Put a call into my mechanic today. He hasn't gotten back with me yet. Hopefully it'll be in his hands NLT tomorrow.
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Your old cylinders will have bronze bushings in the rocker arms. The starter adaptor on the 0-470- will now and again cast off a flake. 1 flake is not a indicator to spend $2500.00 on a overhauled one.
 
timwinters said:
Still don't know how that would help. Both EGT's and CHT's are nil for the first "few moments" after start up on my EI UBG16.

But I'm all ears!

(Mine is the older "non-recording" type).
Click to expand...
You still talking about your ears or your engine monitor.

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teejayevans said:
Why not just pull CBs for sensitive equipment and power up, wait for the boot process to complete, start engine.
BTW, do we really need to be worried about voltage spikes anymore with modern equipment?
Most modern equipment is dual voltage and has voltage regulators built in.



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Because often times the draw from starting shuts them down and they have to reboot.
 
docmirror said:
Not to be too skeptical but wouldn't bits of the inner end of the valve guide go out through the exhaust? It's in the upper cyl air path. Unless there is a fracture in the outer end of the guide, which seems far far less likely. Check for what other components on the inside of the engine are brass/bronze. If it is the outer lip of the guide that things pretty wobbly.
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Can go both directions if the carbon on the valve stem is acting like a file.
 
Or maybe it is because both of us are successful, extremely intelligent and darn good looking. Ah hell it's probably just the name.

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