Cory - I don't know that it will change your plan much and hopefully you're already familiar with it, but TCM Service Bulletin SB03-3 http://www.tcmlink.com/pdf2/sb03-3.pdf provides guidance on your situation, see Table 1. Effectively tells you to do what Barnstormer did, provided you have acceptable leakage. Probably won't change your troubleshooting plan much but may give you some confidence in holding off on pulling the cylinder.

N300RE wrote:Easiest thing to try first is to pressure up the cylinder and hit the exhaust valve with a brass punch or brass hammer. If it's just a small piece of carbon, the air pressure blows it out. If that doesn't work then you have to relap the valve.

right that's staking...

I just got off the phone with Adrian and had a good conversation with him. Adrian runs the same engine as mine in his Bonanza. Here's what he had to say. I'll just kind of regurgitate our conversation, so don't shoot the messenger. I'm just relaying the information in the event it can be useful to the conversation.

He said that leaking exhaust valves primarily are caused by 1) valves not seated correctly due to carbon build up or 2) they have been burnt and warped.

Looking at the pics of my valve, he said that while it doesn't look bad, the inner burn pattern is kind of scattered as opposed to circular like it should be. He didn't mention the outer ring other than that without getting better optics to see the color, he couldn't give me a good analysis on what is going on with it. He said with good optics, it would take him about 2 seconds to give me an opinion on the health of the valve. Anyone know of someone in northern UT with an endoscope?

I asked about staking and lapping. He didn't have much to say about staking. I think he just said it might help.

Regarding lapping, his opinion is that it is one of the worst things you could do. The problem he has with it is that some of the compound will get down on the valve guide and ruin it.

I had provided him all the info of where and how I run the engine. While not being a proponent of LOP ops, he said that if it is done correctly it won't cause burnt valves. From my description he said it sounds like I'm doing it correctly. He said of those engine that he has seen with burnt valves who were running LOP, the cause is the operator not doing LOP ops properly, or it was due to valve guide wear, rotation cap failure, worn rocker arm, or installation imperfections.

He says there are some additives that can be added to help with carbon deposits. I'll leave it at that.

If an overhaul is needed, he says the place he uses out on the east coast runs about $600 for an overhaul as opposed to $1200 for a new cylinder. He said to be sure to include the rocker arm with the cylinder when it is sent in as a worn rocker arm could be the cause. The wear pattern should be square. Also said to look at the rotation cap as it may have stopped doing its job.

So, his recommendations are:

1) Get better optics to be able to discern the color of the valve.

2) Try an additive, similar as was suggested earlier...in theory.

3) Retest the compressions in 10-15 hours.

4) If the leak persists (or if color in step 1 calls for it), overhaul the cylinder.

I spoke with my mechanic and he agrees with Adrian's assessment and plan of action. So, we will see what happens. We will bore scope it again to see if we can get a better read on the color and again around mid October when I hit 10-15 hours.

Thanks for all the input everyone. It's really appreciated. I'll let you all know what happens.

This is just my father of 2, a&p/IA opinion. Save yourself the hassle and the extra time down the the road, pull the cylinder and send it off for overhaul. You'll have it back in a couple weeks and you'll feel great about flying around in the mountains with with your bride and all your little future aviators. I just went down this road in the past year. I lapped a valve and thought it was great and saved a bunch of money. 20 hrs later, I replaced that cylinder and one more. I should have done it to begin with. Piece of mind is worth a lot when you fly with your family.

Jeredp wrote:This is just my father of 2, a&p/IA opinion. Save yourself the hassle and the extra time down the the road, pull the cylinder and send it off for overhaul. You'll have it back in a couple weeks and you'll feel great about flying around in the mountains with with your bride and all your little future aviators. I just went down this road in the past year. I lapped a valve and thought it was great and saved a bunch of money. 20 hrs later, I replaced that cylinder and one more. I should have done it to begin with. Piece of mind is worth a lot when you fly with your family.

Thanks for the info. Yeah, it's basically going to get a one time chance to see if it's just carbon. If not, it will get pulled. I'll be flying some planned flying without the family in the next month, so I'm ok with giving it the last chance.

One stop in oceano is a great quick shop!

Cory - How'd you make out with this? I came across another document that's worth adding to your library if you aren't already familiar, good companion to the TCM Service Bulletin. TCM Service Information Directive 97-2B - http://www.tcmlink.com/pdf2/sid97-2b.pdf

Thanks Vick. I'll check it out.

I'm still trying to find a way to get a better pic of the valve. I've got one more FBO to check out. After that I'm at a loss. Also still working on the 10-15 hours before we will check it again. Probably after HSF.

Just an update on this issue I've been having. Since I last posted, we checked the compression at 25 hours and it had dropped to the low 60s...not too much of a change. We decided to continue with our game plan described above and check it again at the oil change 25 more hours down the road. Two weeks ago I hit that point, did an oil change, and checked the compression again. This time it was down to 51. So, made a call to Western Skyways and am taking the plane down this coming Wednesday to have them take care of it. I'll let you know how it all plays out. I think I'll feel better, and I know Dee will feel better, if we have it done before we get busy flying this summer.

Had the same with O470. Pulled the cylinder and had it rebuilt. Builder called and said to push the throttle handle in a little further from now on. No more cylinder problems after that.

I would steer away from an overhauled cyl. I've never had good luck. I just put a pponked 520 back together. 330hr tt on new eci cyl, and it had two burnt valves and wore guides. Pulled them, brought the cyl to the machine shop, he put the guides in and then took them and had them put the new valves in. Lycon said that it was probably too lean, which caused the problems. Sent them the carb and had it re jetted. Apparently with the gravity feed system the engine doesn't get enough fuel. So we will see what happens.

My 1200-hour factory remanned 470K had a leaky exh valve at annual time. Made 60 / 80 (barely), which is generally considered the minimum. Checked it again at oil change 6 or 8 hours later- now 45/80 & really hissing through the exhaust. Got a borescope and checked the valve action- wobbling around some, plus uneven burn pattern. According to the logbooks, this is the first time a cylinder's been off so I hated to do it, but there's no use in putting off the inevitable. And better now than hafway through the summer flying season. We pulled the cylinder & sent it off to premier in Troutdale for a new guide & whatever else they say it needs. Should be getting it back in a few days.

Someone posted earlier in this thread that the big continentals don't have the guide/valve issues that the smaller ones do, but this is exactly how it went with the O300 in my 170 years ago.

Just a little update. I took the plane down to Montrose on Wednesday. Allen and Stan came to my rescue and flew over to give me a ride home. We met up at Mexican Mountain after I landed at Cedar Mountain to checkout how bad the ruts are. I posted some pics of the days flying over in the "Where Did You Fly Today" thread.

Anyway, dropped the plane off and they called me Thursday with what they found. Valve guides were worn, valve was starting to burn, if I understood him right, he said it had stretched, and they found a broken oil ring on the piston. Ends up the cost to R&R what needed to be done was only $35 less than their overhaul rate, so an overhaul it is. They said that the cam (the part they could see with one cylinder off) looked great as well as the lifters. They said everything else looked good.

Also had a chance to talk specifics with them about how I run my engine...just to see if anything I said, in full disclosure, would raise an eyebrow. I was glad to see that didn't happen and to have them tell me that it all sounded correct and where it should be.

They said the cylinder shop should finish it today and they will put it back on Monday. Now I just have to figure out the logistics to picking it up on the way back from work in JFK on Friday! Any of you Denver guys want to do some flying Friday?!?!

Well, after an evening flight to Den, a night spent in the Denver airport followed by a mid day flight in the Jumpseat on a Dash 8, I made it to Montrose to pick up my plane.

When the cylinder got to their cylinder shop, they discovered a crack in a fin that was progressing towards the cylinder head. With that discovery, they decided to do an exchange with one they had ready on the shelf for the same price. They showed me the crack, the broken oil ring, and the valve. It had some noticeable play in it and the abnormal burn pattern. After 3.4 hours of low level, balls to the wall scenic discovery flight of central to northern Utah, I got the plane home. Here are some pics.

The oil ring was in 4 pieces.


Pretty much #2 on the Anatomy of an Exhaust Valve poster AOPA put out.


Exhaust valve stem.

Dang! Good thing you got that thing out of there and a new shiny one in!

Yeah. I'm glad I did it, especially in light of the crack they found and the broken oil ring.

Now on to the next issue!

hotrod180 wrote:.... We pulled the cylinder & sent it off to premier in Troutdale for a new guide & whatever else they say it needs. Should be getting it back in a few days.....

Update...got the cylinder back about 2 weeks after we shipped it to Premier. They ended up installing a new exhaust guide, new exhaust valve, ground both seats & lapped valves, reassembled with new valve keepers, honed the barrel, and fit a new set of rings. Labor was a flat rate of $275, total delivered price including parts & freight was $730.

A buddy & I pulled the cylinder off, but I had my IA put it back on (with my help). There went about $370, for a total of about $1100 -- more than I hoped for, but considering everything not too bad. Should be good to go for a long time now...or at least til next annual.