Today's Message Index:
----------------------
1. 07:26 PM - Failed intake valve (Tim Shankland)
2. 09:50 PM - Re: Failed intake valve (ron hansen)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Failed intake valve |
As I sometimes tell my wife when I come home from the airport, I had a
little excitement today, she never like to hear that. The excitement I
had about two weeks ago occurred on climb out, I h was at full power and
about 2500 feet about a mile or so from the airport. There was a
distinct change in engine sound with some loss of power and vibration.
After completing the instant 180 back toward the airport I reduced power
and check gauges. Everything was fine, oil pressure and temperature.
Since I still had power and was high I descended to pattern altitude and
landed. The engine continued to run rough but with no mechanical noise.
I was able to taxi back to the hanger. I quick check showed all plug
wires attached and everything looked normal. Coming back the next day I
pulled the spark plugs, None were damaged although the ones on the port
side looked damp. Checking compression the back port cylinder had zero
compression. I pulled of the cowling and rocker arm covers. The valve
train was intact and working, the only change was that the .014 gap on
the exhaust valve was gone. I loosened the adjustment and checked
compression again still zero. Putting a hose the spark plug hole and
blowing I could hear the sound in the carburetor. I order not to have to
take the engine off I build a stand to hold the engine with the top
mounts removed. The attached picture is what I found. The exhaust valve
showed no damage or change but a large piece of the intake valve was
missing. A little shaking of the head dropped the piece out. It had been
blown into the intake manifold in the head and remained lodged there. As
large as it was it might not have been able to come out unless lined up
perfectly. The only mark on the piston or head was a small scratch that
you could have made with a screwdriver. To make the issue more confusing
the other two small pieces in the picture also fell out of the head.
They are aluminum and look as though they had broken off a cylindrical
section but with otherwise undamaged , thus they did not get into the
combustion chamber. My problem is I don=99t know where they came
from. They are not from the head itself, the manifold in not aluminum
and I can=99t find any damage to the carburetor. I recently
replaced the air filters, maybe they were lodged in there. Has anyone
else had an intake valve fail like this. Being cautious I took the other
head off and both are now in the shop having all valves replaced. I have
a little over 300 hours on the engine and there was no evidence of guide
movement. Any experience with this type of failure would be
appreciated.
Tim Shankland
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Failed intake valve |
Tim,
Thanks for the info. I had a valve guide failure at <100 hours. I believe
I was running hotter than I thought due to poor fuel distribution and poor
instrumentation, though it was per Stratus guidelines.
I can't think what the aluminum pieces are in your pic and I've had my
carbs apart, the heads off, and so forth. Sorry, but I'm stumped right
now. Maybe it will come to me.
Nice work getting back safely. It sounds easy, but it's a credit to you
that it sounds easy. That's hugely important to the reputation of
experimental aircraft.
Ron Hansen
On Mon, Dec 19, 2016 at 7:25 PM, Tim Shankland <tshankland@sbcglobal.net>
wrote:
> As I sometimes tell my wife when I come home from the airport, I had a
> little excitement today, she never like to hear that. The excitement I ha
d
> about two weeks ago occurred on climb out, I h was at full power and abou
t
> 2500 feet about a mile or so from the airport. There was a distinct chang
e
> in engine sound with some loss of power and vibration. After completing t
he
> instant 180 back toward the airport I reduced power and check gauges.
> Everything was fine, oil pressure and temperature. Since I still had
> power and was high I descended to pattern altitude and landed. The engine
> continued to run rough but with no mechanical noise. I was able to taxi
> back to the hanger. I quick check showed all plug wires attached and
> everything looked normal. Coming back the next day I pulled the spark
> plugs, None were damaged although the ones on the port side looked damp.
> Checking compression the back port cylinder had zero compression. I pulle
d
> of the cowling and rocker arm covers. The valve train was intact and
> working, the only change was that the .014 gap on the exhaust valve was
> gone. I loosened the adjustment and checked compression again still zero.
> Putting a hose the spark plug hole and blowing I could hear the sound in
> the carburetor. I order not to have to take the engine off I build a stan
d
> to hold the engine with the top mounts removed. The attached picture is
> what I found. The exhaust valve showed no damage or change but a large
> piece of the intake valve was missing. A little shaking of the head dropp
ed
> the piece out. It had been blown into the intake manifold in the head and
> remained lodged there. As large as it was it might not have been able to
> come out unless lined up perfectly. The only mark on the piston or head w
as
> a small scratch that you could have made with a screwdriver. To make the
> issue more confusing the other two small pieces in the picture also fell
> out of the head. They are aluminum and look as though they had broken off
a
> cylindrical section but with otherwise undamaged , thus they did not get
> into the combustion chamber. My problem is I don=99t know where the
y came
> from. They are not from the head itself, the manifold in not aluminum and
I
> can=99t find any damage to the carburetor. I recently replaced the
air
> filters, maybe they were lodged in there. Has anyone else had an intake
> valve fail like this. Being cautious I took the other head off and both a
re
> now in the shop having all valves replaced. I have a little over 300 hour
s
> on the engine and there was no evidence of guide movement. Any experienc
e
> with this type of failure would be appreciated.
>
> Tim Shankland
>
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|