Exhaust valve progression

[grubbat]

I saw a set of Continential cylinders for a Lycoming and I was really impressed. The visual quality of cylinder was good, the pistons already had the rings installed and gapped and oriented in the cylinders. All you have to do is pull the pistons out of cylinders just enough to install the pins and then install cylinders.

Not too long ago, the rings Always had to be installed , gapped, removed, installed, oriented, compressed,blah blah Blah.... not sure if I completely trust this new way but it shows someone is listening on improving the process.

[pa38112]

Scott,
I am curious why you did not pull the cylinder after the first or second photo? I'm 100% for watching conditions to gauge their severity; however, an exhaust valve is one of those things that can fail suddenly and catastrophically. I am not judging - just trying to learn. Also, do you have EGT CHT data and did that show the failure progressing?

[scard]

Originally Posted by pa38112

Scott,
I am curious why you did not pull the cylinder after the first or second photo? I'm 100% for watching conditions to gauge their severity; however, an exhaust valve is one of those things that can fail suddenly and catastrophically. I am not judging - just trying to learn. Also, do you have EGT CHT data and did that show the failure progressing?

I guess all I can say is that we all have different risk tolerances. I like being able to observe the monster that lurks in full view.

[scard]

The cylinder is back on and ready for a test flight this weekend. Not too shabby, AOG only one weekend.
While the #3 cylinder was away on vacation, I took the time to add bypass ducts to the #3 and #2 baffles. I can't wait to see the results of that.

[boom3]

Question because I really don't know...

When a valve like this eventually fails and deems the cylinder dead for power, will the engine make enough power for the airplane to maintain altitude and make it to an airport? Say 10 to 20 miles away? Would it be so rough that you'd have to reduce the power setting and land immediately?

** standard day, standard weight, normal 4 cyl RV, nothing catastrophic...

[vic syracuse]

Usually an engine that ingests a valve is followed shortly by catastrophic failure, but nothing is certain. If just a little peice breaks off of the valve and it is your lucky day the piece just might go out the exhaust on the next cycle and you are left with a rough running engine that might get you to the airport you mention.
Bigger pieces than that will probably get beat around in the cylinder, potentially busting a piston or worse.

[N363RV]

Years ago I had a cessna 150 (continental o200). I was on my way down to houston from the DFW area and the engine began to shake. I pulled it back to idle... switched Left/Right Mags... didn't help. I was lucky that there was an airport just about 3 or 4 miles away and the C150 will glide pretty far too.

After we landed, oil was pouring out of the engine. The valve poked a hole in the piston.

I don't think a stuck valve is much better depending on how open it gets stuck. It can make for a pretty shaky engine. Another guy I know had a cherokee where the valve got stuck and it bent the push rod.

Scott... I'm glad you guys got it fixed so fast. I know it is a drag not having a spare airplane... but I think you are working on changing that. :-)

[tim2542]

Yeah the very first pic shows a green edge indicating very high temps, that I believe ought to be considered a stop sign.
Glad it didn?t come apart on you. How were the guides?
Tim Andres

[scard]

The guide was clearly shot. The morning that we pulled the cylinder, you could clearly see the valve doing a side-step into the seat with the borescope as I rocked the prop open/closed. Now, That gave me the shivers .

I was quite happy with the cylinder shop that it went to (Sal in Prosper Tx). Tanya shipped it on a Wednesday and we had it back the next Tuesday. She said Sal was easy to talk to as well. How about that! Compared to the last one that we sent to ECI, who had it for over a month until I told them that I'm coming tomorrow to pickup my cylinder repaired or not. Woohoo, my pushrods even fit upon reassembly.

Two little work sessions during the week to reinstall and get everything buttoned back up and it is back in the air. I did a couple short test flights over the field yesterday. Happy airplane. Solo, light on fuel, 80deg OAT. It felt like a rocket ship to the above pattern orbit. Oh, and the first early indications of the new baffle bypass ducts on #2 and #3 are very exciting too.

Now for a nugget for "internet fodder". "...indicating very high temps..."? Whether contributing or not, we didn't need an indicator to know that there were very high temps in these cylinders. We know for sure that there were, given a lightspeed ignition that failed to max advance (42deg) and was flown for at least a few flights before we figured it out. That event was probably about 40hrs before the first picture in this thread... However, this cylinder was already on it's way (exhaust leak) before that.

[BillL]

Good to hear that there was not heat damage to the seat or head. The extra heat can crack seats and heads.

Which one is next?