Finding a mechanic to lap a valve

[gdwinc]

When I change the oil on my Ovation I pull a spark plug from each cylinder and take some pictures with a borescope.  My last round of pictures shows that the exhaust valve on my #4 cylinder is showing a bit of asymmetry. 

I had thought getting the valve lapped in place was a pretty common maintenance task, but A&Ps at two different shops that I have used in the past aren't interested in lapping the valve.  One said that he doesn't believe in borescope pictures on high time engines (I'm right at TBO) and it isn't worth doing the work.  The other said that it is a lot of labor and his recommendation is to wait for the cylinder to fail a compression test and then replace it.

I'm based in Salt Lake City, so my real question is if any of the other Utah based pilots have an A&P they would recommend.  If you have a suggestion for an A&P please let me know.

My other questions are whether or not anyone else has faced this issue, and if you think I'm off base in lapping a valve on an engine that is at TBO.

 

[KSMooniac]

I think you're trying to do something very prudent to extend the useful life of your engine, assuming all of the rest are still checking out well.   Waiting for it to fail is some of the worst advice I've read in a long time!  And you obviously know TBO is just a recommendation and there is no good reason you can't keep flying it as long as it is airworthy.

Many years ago I flew to my semi-local engine shop and had them ream some valve guides for me that had gotten tight and caused some sticking.  I scheduled in advance and they did it while I waited.  You might have to find a cylinder or engine shop near you since a lot of modern A&P's are part-changers instead of mechanics, unfortuantely, and get queasy if you ask them to disassemble anything related to an engine beyond an accessory.

Savvy/ @kortopates might have a lead for you?

[gdwinc]

@KSMooniac Thanks for the response.  I should have mentioned that I am a Savvy customer and they provided options for more accommodating shops.  The recommendations were in Grand Junction, CO and Boise, ID so not the most convenient, but doable if there aren't any local Salt Lake area options.

[philiplane]

Lapping is worthwhile on engines with less than 1500 hours because you're generally just removing junk from the seat to restore the seal, and the guide has minimal wear.

But with high time engines, the valve guide wears enough that the valve no longer seats on center, leading to the hot spot on the weakest contact area. This is not fixable by lapping.

If you're on oil analysis, you will see a rise in nickel if the guide is wearing. Or, you can pull the rocker cover and check the valve stem wobble directly. If it wobbles, lapping is a waste of time.

So if you're at 2000 hours, the odds of lapping being successful are slim. 

Edited July 14, 2023 by philiplane

[Caz]

Not sure I understand the level of thinking of your mechanics.   It's not that much work.  Certainly not as much as changing out a cylinder.  For people who say they are over-worked and under-paid, I sure do hear a lot of mechanics wanting to put off the simple stuff until the simple becomes much harder. 

I would do the in place lap in a heartbeat over pulling a jug.  Unless of course there are other indications that would indicate that it would not be of any benefit. 

Just my 2 cents.

 

 

Edited July 14, 2023 by Caz
added a condition

[gdwinc]

6 minutes ago, philiplane said:

Lapping is worthwhile on engines with less than 1500 hours because you're generally just removing junk from the seat to restore the seal, and the guide has minimal wear.

But with high time engines, the valve guide wears enough that the valve no longer seats on center, leading to the hot spot on the weakest contact area. This is not fixable by lapping.

If you're on oil analysis, you will see a rise in nickel if the guide is wearing. Or, you can pull the rocker cover and check the valve stem wobble directly. If it wobbles, lapping is a waste of time.

So if you're at 2000 hours, the odds of lapping being successful are slim. 

@philiplane Thanks for this info about lapping a valve on high time engines.  Before I bought the plane, the engine had a top overhaul less than 800 hours ago.  So while the engine is at TBO the cylinder itself doesn't have all that many hours. 

[PT20J]

There are three types of maintainers in my experience: Old timers that don't believe in lapping, reaming, LOP, etc. Youngsters that don't have experience other than removing and replacing parts. And finally, the experienced professionals that pride themselves on good diagnostic skills and the ability to perform the least intrusive fixes. If you find one of the latter, take good care with them and pay them well.

[KSMooniac]

800 hour jugs should be good candidates for lapping, but if they were factory-new TCM cylinders, then you might be just starting to experience their sub-par valve installation consequences that are well-documented on beechtalk.  They aren't installed as well as a good engine shop can do when they take the time to do it right, and the valves & guides eventually wear unevenly and need attention.  Consensus from my years of reading/observation is that 700-900 hours is typical for modern TCM jugs (post-2000 or so), no matter if you're a LOP or ROP operator.  The expert TCM engine shops like Powermasters in Tulsa will routinely take new TCM jugs out of the box and re-work all of the valves before installing them, and those typically have no issues over a full TBO run.

Having said all that, if it is just one, and you've been watching all of the others, then it very well could be worth the effort to lap that single one.  If you get another one in the not-too-distant future, then it might be time to think about something more serious.   I would call one of those recommended shops and see if you can get a while-you-wait appointment I did, perhaps on a Monday or Friday, and make a little weekend trip out of it.

[ArtVandelay]

I’ve found APs don’t want to do anything more than what’s required at annual once engine gets to TBO.

[M20F]

All I would say is you need to know what you are doing to lap a valve or you are going to make a mess.  That being said it isn’t super difficult for hanger fairies.

 https://airplaneownermaintenance.com/109-exhaust-valve-problems-could-lapping-be-a-good-option/

[kortopates]

First i have to disagree that it’s not worthwhile to lap a valve in a high time cylinder. That’s nuts. How to do you suppose Mike B got to 3500 hrs on his engine cylinders? Sometimes the valve can’t be corrected by lapping and the cylinder has to come off for repair but it’s always worth a try to lap it and see if you can correct it. It sure beats pulling the cylinder every day. We’ve found no correlation to worn valve guides causing compression issues or burning of valves, contrary to what many people think. And if your patient you can restore a virtually zero/80 compression, due to leaking exhaust, to 75+/80 cold. It will take a good 15 hrs in service to verify its a winner but who wouldn’t want to try that first.

For how to do it, see Mike’s youtube Savvy Aviation video on valve lapping: 

Sent from my iPhone using Tapatalk

Edited July 15, 2023 by kortopates

[N201MKTurbo]

One of my new Continental cylinders for my Lycoming had a leaky exhaust valve. I removed the keepers and springs using the rope trick and a homemade spring compressor. I was intending to spin it with a hand drill, but couldn't get it on. I just oiled the valve and spun it with my fingers for about 20 minutes. That's how long it took my fingers to get sore. I put it back together and the compresson went back to 80/80 and it has been fine ever since.

[Red Leader]

Wait, Continental cylinders for your Lycoming? Can you do that?

[Ragsf15e]

40 minutes ago, Red Leader said:

Wait, Continental cylinders for your Lycoming? Can you do that?

Yes. Continental and lyc are the only ones that make angle valve cylinders (new) for the io-360.

[PT20J]

1 hour ago, Red Leader said:

Wait, Continental cylinders for your Lycoming? Can you do that?

Continental bought ECI. ECI made Lycoming PMA cylinders. You are not putting Continental engine cylinders on your Lycoming.

[rickseeman]

Keep looking until you find someone that will work with you on this. There are so many good videos for help. It isn't like the old days. (This time it's better.) It can be done. It will be fun and educational. Since you aren't an A&P I would never suggest that you and a very mechanical friend, with a lot of tools, can do it. You know that would be against the regs. Do a compression test and a leak down before and after.

[Utah20Gflyer]

Have you tried asking the engine shop at the bountiful airport?  I don’t have any  personal experience with them but have heard good things. 

[gdwinc]

10 hours ago, Utah20Gflyer said:

Have you tried asking the engine shop at the bountiful airport?  I don’t have any  personal experience with them but have heard good things. 

@Utah20Gflyer I have not contacted that shop. I think it’s called Precision Air Power. I’ll give them a call tomorrow. Thanks for the suggestion!

 

[gdwinc]

Precision Air Power at Bountiful is a no-go. They only work on cylinders when pulled from the engine.  Do any of the other Utah folks here have suggestions for an A&P who would be willing to lap the valve in place?

Thanks! 

[JimB]

The problem may be that there is no official procedure published by Continental to lap a valve in place. I fully understand that it is common practice and it actually makes sense to do it but your A&Ps may be reluctant to do it without some reference material. 

[Utah20Gflyer]

On 7/17/2023 at 4:25 PM, gdwinc said:

Precision Air Power at Bountiful is a no-go. They only work on cylinders when pulled from the engine.  Do any of the other Utah folks here have suggestions for an A&P who would be willing to lap the valve in place?

Thanks! 

Have you asked Huy at Advantage Aviation?  He has people who could do it but the question is whether he could fit you in.   It can be a challenge to get your plane into his shop for work.  

[mhrivnak]

I found similar reluctance after noticing an obvious hot spot with a borescope in an IO-360. It seems like it will take more time for valve lapping to become something that an average A&P feels comfortable with. Thankfully it's an easy flight from here up to Shenandoah Valley, and I was able to get Dean Showalter (a big proponent of valve lapping via his podcast) to do it. I arrived in the morning, and he was done before lunch.

At the next annual, compressions and borescope views were stellar. I recently had another borescope view after about 70 hours, and it looks just as you'd hope; no sign of the hotspot or any other concerns. The cylinder is more than 30 years old with ~2300 hours. I figure that changing the cylinder would be around 10x the cost, so lapping was worth a try, and it will only take 100-200 hours of extended life to easily justify the cost.

[gdwinc]

2 hours ago, Utah20Gflyer said:

Have you asked Huy at Advantage Aviation?  He has people who could do it but the question is whether he could fit you in.   It can be a challenge to get your plane into his shop for work.  

Huy was the first one I called. He was the tech who told me it’s not worth the labor and to fly with the valve as is until it fails a confession test. 

The good news is that I found a tech to do the job - Mike at Scud Air Solutions at KOGD. I have an appointment next week. Just for fun, I’ll endeavor to update this thread with a before and after pic of the valve after it gets some hours following the lap job.
 

 Thanks to every who offered suggestions and advice. It is much appreciated!

[A64Pilot]

On 7/18/2023 at 9:41 AM, JimB said:

The problem may be that there is no official procedure published by Continental to lap a valve in place. I fully understand that it is common practice and it actually makes sense to do it but your A&Ps may be reluctant to do it without some reference material. 

Ding, we have a winner.

There are quite a few “procedures” it seems that are being recommended by other than the manufacturer.

Problem is a mechanic isn’t allowed to just do anything they please, they need as a min data that’s acceptable to the administrator, often when specific instructions don’t exist that’s AC 43.13. You cant just decide in your opinion that the new Velcro is excellent for attaching inspection panels for instance, silly example and it was meant to be, but it’s what keeps some idiot from reskinning a wing and using PK screws instead of rivets for example, because you know PK screws are steel and stronger than rivets, so therefore better.

This is how it plays out, I lap a valve, later that valve breaks off its head which has nothing to do with me lapping it, but I’m in court trying to explain how there’s this guy named Savvy on the internet that says it’s the way to go, while the person’s Lawyer who is suing me looks at the jury and says if I had replaced the valve like the manufacturer requires, this accident wouldn’t have happened.

In your opinion, what do you think will happen? Think no one will sue over a $50,000 engine or crashed aircraft?

At least you’re searching for a mechanic. I think many don’t, that’s why step by step DIY videos are posted on the procedure.

Your doing the right thing.

Many will say Lycoming doesn’t care, only wants to sell new parts etc., but you know the “rope trick” is an approved published procedure by Lycoming.

 

 

 

Edited July 19, 2023 by A64Pilot

[Pinecone]

7 hours ago, A64Pilot said:

This is how it plays out, I lap a valve, later that valve breaks off its head which has nothing to do with me lapping it, but I’m in court trying to explain how there’s this guy named Savvy on the internet that says it’s the way to go, while the person’s Lawyer who is suing me looks at the jury and says if I had replaced the valve like the manufacturer requires, this accident wouldn’t have happened.

Except the shop is not saying to replace the valve.  Or at least one shop.  They are saying to keep flying it until something bad happens.