Cylinder Troubles, Deep Poop

[bjb3013]

I have a Lyc IO360-A1A, cylinders 25 Hrs since OH.
Thursday AM I took off for SNF. About 30 seconds into the flight I noticed a slight surging. It smoothed out so I circled the airport and found that #4 egt was really low. Surging continued getting worse. I landed and swapped plugs . Now running on the ground with 3 cylinders and shooting fire out of the exhaust . Pulled the plugs and looked in the holes with a flash light. Now I really get the **** scared out of me. I see a 1/2 circle imprint of the intake valve on the piston top ???

Pulled cylinder today. Seems the intake valve seat came totally out of the head and is wedged under the valve. What causes this? The piston is bashed up, but the only thing I see wrong with the cylinder is the seat and the bent valve. Can't see any cracks. How should the cylinders be checked during OH to prevent this ? Is it possible to fix this? Now I am wondering about the other 3.

BB

[tin man]

ECI cylinders?
Tom

[bjb3013]

Lyc nitride

[frankh]

The only way that wuld happen is if there was not enough of an interference fit between the seat and the head.

They should be heat shrunk in there....I.e seats are physically bigger than the hole, the head heated, seat chilled and the two are mated.

I've never heard of this happening, then again I have not been around airplane mototrs that long.

Well I would say Lyc owes you a set of 4 cylinders and then you need to ask what the likely hood of the rod bearings being trashed as well?

They maybe fine but you need to get Lyc's take on this to start.

What a bummer!

Frank

[gmcjetpilot]

If there was no metal its just a jug and piston change. That is pretty cool. Not sure if there is anything to do with the rod big end? I'd call them for sure.

Try changing one rotor on a mazda or cylinder on a subaru while its still mounted on the plane. It also got you back on the ground. Aces. Sorry for you troubles. Never heard of this problem or what would cause the seat to become dislodge. Its pressed in to beat the band.

It just goes to show a Lyc can take a beating and keep on ticking.

Where they used OH cylinders or new? Who did the cylinder overhaul or what brand of new was it?

Glad you, your plane and most of your engine is OK

[LifeofReiley]

Originally Posted by tin man

ECI cylinders?
Tom

And what does ECI cylinders have to do with anything?

[Rivethead]

Yea I was thinkin the same thing. What does ECI have to do with it? This kind of problem comes from high CHT. Usually, Sometimes.

[az_gila]

Originally Posted by Rivethead

Yea I was thinkin the same thing. What does ECI have to do with it? This kind of problem comes from high CHT. Usually, Sometimes.

Yes... and if they were poorly overhauled, it could have been the previous lifetime's high CHTs...

If it was a Lycoming factory overhaul (their terminology) - then it had new cylinders put on it.

Who did the OH?

gil in Tucson

[DanH]

<<Seems the intake valve seat came totally out of the head and is wedged under the valve. What causes this?>>

In general, incorrect interference fit. The minimum is around 0.0065", max around 0.010", meaning the OD of the valve seat ring should be 0.0065" to 0.010" larger than the machined hole in the head casting.

<<The piston is bashed up, but the only thing I see wrong with the cylinder is the seat and the bent valve.>>

I'm a conservative, but a bashed piston would push me to a full teardown for a magnaflux check of rod, pin, crank and crank gear.

<<Can't see any cracks. How should the cylinders be checked during OH to prevent this ?>>

You would need to remove the valve seats; no other way to check an installed interference fit.

Since yours has uninstalled itself, you have the opportunity for a little forensic measuring. These are 25hr cylinders? My long-distance guess is that your cylinder had a seat replacement during overhaul. Seats come .010", .020", and .030" oversize. The overhauler removes the old seat, does a clean-up cut in the head recess with the proper oversize cutter, and installs a new matching oversize seat. If, for example, somebody with a hangover cuts the recess with a .020 cutter and installs a .010 seat, it would probably stick enough to get through the subsequent seal face cut and assembly.

Soooo, measure your seat bore ID and the seat OD. If they don't match the dimensions in the Lyc manual, I'd be having a chat with the factory.

[frankh]

There is no way this is any kind of acceptable...I would leaning towards the complete engine strip as well...Remember the seat got squished between the piston and head...This (large) metal crunching load got transferred all the way to the crankshaft.

This need to be paid for by whoever provided those cylinders.

Frank