Good Morning Guys,
As most of you may know On my way to landing at the Virginia Regional Fly Inn I
suffered a engine malfunction. While the engine was indeed running rough, I was
able to quickly identify the cylinder that was in-distress and made several
tries at correcting the problem from cockpit controls by varying throttle and
mixture. I was still producing power and was able to accelerate and climb. I
made the decision to land normal nd not screw u the pattern that was very busy.
I was able to taxi to a parking spot and shut down all with out anyone else
being aware that I had a issue.
On the ground it was determined that there was no compression at all in
the center passenger side cylinder.
I made the decision to truck N357CJ home.
This brings us to the forensics of the problem. I did a static leak test
and found it to be a full leak thru the intake. I also could see the valve seat
thru the spark plug hole. I pulled the head off and was able to see exactly
what was suspected. The valve seat had come completely out and turned some what
sideways and the valve had beat the seat into the head. As i understand this is
something that happens to the corvair occasionally.
The most important information i am leading up to here are the signs
that I pretty much ignored that might have prevented as much damage and
certainly saved a $1000 in travel expenses.
A couple weeks before the trip to Virginia i had changed the spark
plugs. The actual event of the valve seat becoming loose may or may not have
happened either right before i changed plugs or the very next flight after. In
any case I did not notice the temperature change until the first flight after
changing the plugs. The front cylinder on the right bank had a higher temp than
normal by 20 to 30 deg. The middle cylinder head temp was lower by 90 to 100
deg and the rear cylinder head temp was normal. I had put this info out on the
net and got a couple responses that I had not considered and that was that I
may have damaged the temp sensors. I had not thought that I damaged them but
became more nonchalant about the problem. The other thing was that i had more
trouble getting consistent exhaust temps. And in fact the entire bank of temps
would switch from one bank to the other as far as the high exhaust temps with
changes in throttle settings and even change when sett at one setting for 3 or
4 minutes at a time.
I present this information for everyone else to learn from.. I have a
full set of instruments to draw information from. I did not properly process
the information I received from them. For those that do not have full sensors I
believe that you are putting yourself at a disadvantage to start with but would
give you an excuse for not realizing a problem. For the pilots that do have
full engine monitoring i would strongly encourage vigilance in processing the
information that is presented. I should have verified the probes were indeed
faulty or not. Then I would have known that something was amiss. I still may
not have known what so I am saying now that if you experience a low cylinder
head temp that can not be changed by throttle settings or mixture changes you
should certainly consider that you may be on the way to loosing a valve seat.
As a side note I burn 100ll all the time. when i had the heads off at
280 hours there was a very thick build up of lead on the entire combustion
chamber. At this time there is over 200 hours on the cleaned up combustion
chamber. There is again a lead deposit but not near a bad. More like 20% as
much as it was 2 years ago. The difference is only that i have been using
Marvel Mystery Oil in the fuel. Not by any means a scientific test nor am I
encouraging the use. Merely stating that I am trying it and it seems to make
difference. The worst part of the lead is that it is attaching to the valves
and making deposits on the seats that probably keep them from sealing
completely at some point in time.
I'm not sure how I am going to have the head problem resolved yet or
when i will get to give a flight report again but it won't be that long til
I'm free to time travel again.
Joe Horton, Coopersburg Pa.
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