Today's Message Index:
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1. 06:35 AM - RV10 Fuel Flow Gauges (Doc)
2. 02:58 PM - Re: Electric Fuel Pump (Coop85)
3. 02:59 PM - Exhaust valve leaking (Coop85)
4. 03:46 PM - Re: Exhaust valve leaking (Tim Olson)
5. 06:56 PM - Re: Exhaust valve leaking (Coop85)
Message 1
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| Subject: | RV10 Fuel Flow Gauges |
Guys: We have built Two RV10s over the past 9 years N123CV & N784DC.
We fly both of them regularly. One INDICATES 14.5 gal/hr at 24 squared
(6500 feet) and the other 15.5 gal/hr. They are actually burning 11
gal/hr. We gust set each plane where we have found out where it needs
to be (the old thin to rough then smooth and watch the exhaust gas
temp). When we installed our Fuel sensors in each tank, we adjusted
them so that they read Empty when there is 3 gal in each tank, not that
you don't want to keep track of your fuel burn, but it is a little
reasuring to see the gas gauges wiggle a little when you rock the
wings. Doc
Message 2
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| Subject: | Re: Electric Fuel Pump |
Thank for the recommendations to contact Don at Airflow Performance. He was exceptionally
helpful and replaced my fuel pump including a small mod to use on
my current setup for HALF the price Van's is asking!
Marcus
--------
Marcus Cooper
RV-10 since 2006
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497955#497955
Message 3
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| Subject: | Exhaust valve leaking |
I have a clear leak in one of my exhaust valves while doing a compression check.
The odd thing is I seem to have normal power and the temperatures are all consistent
with the other cylinders. Just curious if anyone has had this and any
easy solutions? I've read a few links about sticky valves and a rope method
to help free them but I'm curious if there are other thoughts.
Thanks,
Marcus
--------
Marcus Cooper
RV-10 since 2006
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497956#497956
Message 4
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| Subject: | Re: Exhaust valve leaking |
Hi Marcus,
A couple things...
The rope method is just about getting the valve spring off, as far as I
know. I don't think it's actually useful to help unstick a valve.
And of course valves can be sticky, or wobbly...likely not both
at the same time.
What you probably have going on is just a bad seating of the valve
that's causing it to leak. I dealt with that this spring, and found
it really isn't that hard to fix, or inspect, as long as you've got
the tools.
You will need a valve spring compressor tool for sure.
The one I have is this one:
https://www.aircraftspruce.com/catalog/topages/compressor.php?clickkey=8804
It's also helpful to have a little light. Either a flashlight into
the cylinder, or one like this:
https://www.amazon.com/gp/product/B00008BFS6/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1
You can do it without dropping the exhaust, if you wish. I have a
friend who may jump in on the discussion who just started this on
his engine yesterday. He dropped his exhaust. I didn't.
As a side note, I got a rocker arm removal tool that compresses the
springs, and my buddy tried his yesterday and didn't like it.
Certainly a made-for-the-task tool to compress both springs would
make the job a piece of cake.
At any rate, you basically just remove the rocker cover, then
remove the rocker arm from the exhaust valve side, and then
remove the valve spring (using the rope trick) and then you
will be able to push the valve into the cylinder far enough that
you can spin it with your fingers and inspect the seating surface.
If it's seating all the way around it should be pretty uniform
looking of a darkened stripe around the valve seat where it makes
contact. If it's got lighter patches, or a narrowing in an area
of the valve, then it's probably just leaking in that spot a little.
To get that seat restored to a nice full seat, you can lap the valve,
right in place. This article is one I found when I was reading on it
and I found it helpful.
https://www.tennesseeaircraft.net/2011/11/13/exhaust-valve-lapping/
There are other good articles out there as well.
Anyway, now that I know how to do it, it's a job that I could
probably get completed in an hour or so. I had slightly low
compression (around 65) on one valve and saw the seat had one area
where the seating wasn't perfect. After lapping it for a short
time, I was able to clean it up and did a cold compression test
and it was >75. I flew it to warm it up, and compression was
back in the normal 77-79 range and stayed there after that.
I know what they say, that compression in the 60's can be
OK on a lycoming, but I would think if you have an outlier on
your engine, you will do yourself a favor if you just deal with
it early, so the seat doesn't get additional erosion.
Hopefully that gets you on the right track to get started.
You can probably see it with a good inspection cam without
pulling the valve spring, but I find that you can get a perfect
view if you just do the little extra work to get that far.
Regarding your comment about normal power and temps, let me
tell you this: I had a worn valve guide on one cylinder
and the valve would barely hold any compression at all.
I was shocked that I even had an issue, because when I did
the warm up flight before the compression test, I watched
my EGTs and CHTs closely and everything ran just fine. Power
felt good, engine was smooth. Nothing identifiable. Then
I did the compression test and found that one valve at 65-ish
and the other way lower, and about had a heart attack.
That's when I learned to lap the one valve, which took care of
it completely, but the other required a new valve guide, done
by a professional shop. They turned it around in 2 days and
did a fantastic job, but they showed me the valve from the
inside of the cylinder perspective before they fixed it, and
it was so wobbly that I don't know how it could have seated.
What that experience told me is that these engines really
won't feel very different, even if you have a big leak.
There was no sign that I could find, at least without paying
close attention. I did find during diagnosis that if I
pulled the mixture back WAY far on the ground for a run-up
I could actually see that one cylinder depart from the others
a little in how the EGTs looked, but you really had to look
hard at it, and that was a real bad leak. So if you have
just a minor reduction in compression, you're probably not
going to have a clue, even with a good engine monitor.
Another side note: Actual A&Ps told me to just put
Marvels Mystery Oil in it and fly it hard. While I understand
their perspective, I'm not the type to just do something
so crude, when I can do a little more work and figure out
the actual issue. That's what led me to learning how to
lap the valve. And, I thought I just had to lap 2 valves
and I'd be all set, but it was very obvious when I pulled
that spring off the very bad compression cylinder that the
valve guide was shot. So I'm glad I didn't just listen
to the MMO tip and go on my way. All the other valves
were both seating well, and had valve guides that had
much more normal clearance, so in the end, all was real good.
One final tip. If you do take off both rocker arms,
make sure you set aside your intake and exhaust rockers
and pushrods in separate places so you get them back
properly on the right position. On many engines, the
only rocker arm with an oil passage is the exhaust rocker.
You want that to get back on that valve. And, the pushrods
are tuned by length, so don't mix them up or you may get
valves that don't open the amount that they were originally
set up for.
Sorry that got long, but there's a lot of info in there to
chew on.
Tim
On 8/24/20 4:58 PM, Coop85 wrote:
>
> I have a clear leak in one of my exhaust valves while doing a compression check.
The odd thing is I seem to have normal power and the temperatures are all
consistent with the other cylinders. Just curious if anyone has had this and
any easy solutions? I've read a few links about sticky valves and a rope method
to help free them but I'm curious if there are other thoughts.
>
> Thanks,
> Marcus
>
> --------
> Marcus Cooper
> RV-10 since 2006
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=497956#497956
>
>
>
>
>
>
>
>
>
Message 5
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| Subject: | Re: Exhaust valve leaking |
Thanks Tim!
As always you are a wealth of helpful information.
Marcus
--------
Marcus Cooper
RV-10 since 2006
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497963#497963
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