Morning Sickness?

[slowflyin]

Good afternoon,

I've been working an issue with my Bravo and as always, I'm reaching out to the group for advice.

M20M  TIO540AF1B    300 hours SMOH  (Victor Aviation) 

On 4/18 I experience a rough running engine after start up.  After 30-45 seconds it cleared up.  The remainder of the flight was ops normal. 

Next two flights were normal as well.  As my annual is coming due I performed a 100 hour on the engine.  This included plug cleaning, testing, and rotating-timing check-and borescope.  Post maintenance I started the engine to check for leaks and experienced the same roughness for roughly twice as long.  My Son observed rhythmic puffs of black smoke and the data shows #1 and #2 EGTs slow to rise.  After the roughness cleared up the engine ran normally.  

#1 Valve

 

Edited Monday at 09:51 PM by slowflyin

[KSMooniac]

I'd start with reaming the guides... McFarlane sells special reamers for this task and it can be done with the cylinders installed.  I had similar events early in this TBO run and had my local engine shop do it and have not had problems since.  /knocking on wood

[Fritz1]

Interesting, I am wondering about this myself, I bought the Bravo with a 200h factory reman engine, used Shell W100Plus until about one year ago and then went to Phillips 20W50 Victory against the advice of my A&P IA, immediate change in oil consumption, two bottom plugs that were typically oiled up became bone dry all of a sudden, either the Phillips is a much better oil or leaking valve guides coked up so they are not leaking any more, I do not have any sticky valves yet, thinking about going half half, W100Plus in Summer, Phillips in winter, the Lycoming appears to be prone to coke up valve guides with certain oils, just can't quite put my finger on it

[EricJ]

My engine has done the occassional morning sickness for years.   An acquaintance that has been in the aviation lubrication business for a long time suggested that going back to W100Plus would likely help eliminate the problem.   I'd switched from W100Plus to W100 a while back for reasons that I don't recall (something about undesirable side effects of the additive), so it may be worth trying.

 

[philiplane]

the type of oil used is irrelevant when it comes to sticking exhaust valves. Lead sludge is the culprit, in combination with a valve to guide clearance that was set at the tight end of the range during overhaul. Cleaning the guides is the remedy. Going forward, you can use Camguard or Avblend to help keep lead sludge from forming on the stems. Camguard with Phillips XC20W50 is preferred for turbocharged engines since it helps the manifold pressure regulation circuit work better throughout the temperature range. Single weight oils promote controller overshoots until fully warmed up.

[slowflyin]

Thanks for the responses.

I use 20/50 with camguard.  Oil consumption is minimal.  I believe reaming the guide is the solution but it's great to hear a consensus.  I'm a Savy user and they offered the same response.  To bad I don't have the appropriate size reamer in my box.  Mcfarland is out of stock.  I plan to back order and clean the valve stem up to buy myself some time.   I don't want to waste time doing the job twice but without the reamer I don't see I have an option.   They estimate 15 June but since COVID I've much more skeptical.   Thanks again.

[Hank]

29 minutes ago, slowflyin said:

I believe reaming the guide is the solution but it's great to hear a consensus. . .  To bad I don't have the appropriate size reamer in my box.  Mcfarland is out of stock.

Check the standard industrial equipment sites for the reamer, you only need to know the diameter. Try McMaster Carr (mcmaster.com) or MSC (mscdirect.com), I've bought a lot of drills, end mills and reamers from both of them over the years. 

Not being aviation houses, they need actual sizes, not just "Continental IO-520 valve guide reamer." Should work nicely for you. If you need tapered readers, they also sell those, or can custom grind one usually in just a couple of weeks.

[slowflyin]

4 minutes ago, Hank said:

Check the standard industrial equipment sites for the reamer, you only need to know the diameter. Try McMaster Carr (mcmaster.com) or MSC (mscdirect.com), I've bought a lot of drills, end mills and reamers from both of them over the years. 

Not being aviation houses, they need actual sizes, not just "Continental IO-520 valve guide reamer." Should work nicely for you. If you need tapered readers, they also sell those, or can custom grind one usually in just a couple of weeks.

Thanks!

[Fly Boomer]

48 minutes ago, slowflyin said:

I believe reaming the guide is the solution

You might want to read what McFarlane says about "reamers":

While using standard reamers to clean valve guides, you probably have noticed that you have some valve guide metal in the reamer flutes afterwards. This metal is cut from the sides of the guide when hard carbon deposits displace the unguided reamer from the original guide hole, or the reamer was not started in alignment with the guide hole. Wavy or gouged guide holes cause premature carbon buildup, poor heat transfer, and early guide hole wear. Prevent damage to your valve guides by using McFarlane Cleaning Reamers!

The patented McFarlane cleaning reamers have a pilot the same size as the valve stem. This properly sized pilot forces the reamer cutter to start straight and follow the correct valve stem path through the guide hole. Finally, a tool that is designed for the job!

https://www.mcfarlaneaviation.com/products/categories/all-products/tools/valve-guide-cleaning-reamers/?page=551&sort=order_a&gad_source=1&gad_campaignid=21898364531&gbraid=0AAAAAD9ZxAk8_KfxOWsVrnpwbJ4dLj_El&gclid=EAIaIQobChMIu7Tq9cSgjQMV507_AR0DJBL_EAAYASAAEgKcG_D_BwE

[slowflyin]

5 minutes ago, Fly Boomer said:

You might want to read what McFarlane says about "reamers":

While using standard reamers to clean valve guides, you probably have noticed that you have some valve guide metal in the reamer flutes afterwards. This metal is cut from the sides of the guide when hard carbon deposits displace the unguided reamer from the original guide hole, or the reamer was not started in alignment with the guide hole. Wavy or gouged guide holes cause premature carbon buildup, poor heat transfer, and early guide hole wear. Prevent damage to your valve guides by using McFarlane Cleaning Reamers!

The patented McFarlane cleaning reamers have a pilot the same size as the valve stem. This properly sized pilot forces the reamer cutter to start straight and follow the correct valve stem path through the guide hole. Finally, a tool that is designed for the job!

https://www.mcfarlaneaviation.com/products/categories/all-products/tools/valve-guide-cleaning-reamers/
 

Thanks, I had read this.  I'm ordering but preparing for plan B.  

[slowflyin]

Well, no joy.  Pulled the valve springs and the valve stem is smooth as silk in the guide.   

[EricJ]

3 hours ago, slowflyin said:

Well, no joy.  Pulled the valve springs and the valve stem is smooth as silk in the guide.   

Did you try both intake and exhaust?   It can be either one.

[slowflyin]

Yes, but thanks for the advice.  

[A64Pilot]

17 hours ago, slowflyin said:

Well, no joy.  Pulled the valve springs and the valve stem is smooth as silk in the guide.   

You should still ream them, but do so slowly to keep a smooth finish, they may just be tight, it happens. Ideal world valve guides are honed not reamed, the finish is important.

A Sodium filled valve runs cooler, it does so by transferring the heat from the head to the stem better, the stem then transfers the heat to the head of course, but the stem in a sodium filled valve runs hotter than an unfilled one as metal expands with heat, if you run LOP as I do your EGT is higher than ROP which could run a valve slightly hotter. It’s though that Lycomings are more susceptible to sticking valves due to sodium filled valves.

Not taking away from LOP, as I said except for high power I run LOP myself.

Sticking valves can lead to bad outcomes

Edited Wednesday at 02:12 PM by A64Pilot

[slowflyin]

Starting to feel like I'm hunting Zebras with regards to the valves.  Both intake and exhaust are smooth with the appropriate wobble.  I had another A&P take a look and I did not offer an opinion prior to his diagnosis.   He concurred all is well.  I also uploaded a video and pics for Savy to diagnose.  Same.   I bought these jugs new from Lycoming and sent them directly to Victor for valve work.   I'm reluctant to ream just for the sake of  reaming as I'm in the do no harm camp.  I may come back to the valves but for now I'm starting to re-diagnose.  Thanks again for weighing in!

[gabez]

On 5/12/2025 at 2:50 PM, slowflyin said:

Good afternoon,

I've been working an issue with my Bravo and as always, I'm reaching out to the group for advice.

M20M  TIO540AF1B    300 hours SMOH  (Victor Aviation) 

On 4/18 I experience a rough running engine after start up.  After 30-45 seconds it cleared up.  The remainder of the flight was ops normal. 

Next two flights were normal as well.  As my annual is coming due I performed a 100 hour on the engine.  This included plug cleaning, testing, and rotating-timing check-and borescope.  Post maintenance I started the engine to check for leaks and experienced the same roughness for roughly twice as long.  My Son observed rhythmic puffs of black smoke and the data shows #1 and #2 EGTs slow to rise.  After the roughness cleared up the engine ran normally.  

#1 Valve

 

reach out to savvy. great service and very easy to work with 

[MikeOH]

5 minutes ago, gabez said:

reach out to savvy. great service and very easy to work with 

^^^ THIS ^^^

[A64Pilot]

On 5/14/2025 at 10:32 AM, slowflyin said:

Starting to feel like I'm hunting Zebras with regards to the valves.  Both intake and exhaust are smooth with the appropriate wobble.  I had another A&P take a look and I did not offer an opinion prior to his diagnosis.   He concurred all is well.  I also uploaded a video and pics for Savy to diagnose.  Same.   I bought these jugs new from Lycoming and sent them directly to Victor for valve work.   I'm reluctant to ream just for the sake of  reaming as I'm in the do no harm camp.  I may come back to the valves but for now I'm starting to re-diagnose.  Thanks again for weighing in!

Understood, my main point is to keep looking.

However if the reamer is of the right size and the guide is also correctly sized the reamer won’t do anything, it will only remove metal if the guide is undersized, but I understand if it ain’t broke, don’t fix it.

Try this, exchange the plugs with another cylinder, it’s rare but sometimes you just get a “bad” plug, one that fires correctly when hot but not so much when cold, if it’s a bad plug then the problem will move to the other cylinder. 

This is unlikely, but it costs no money, is easy and does no harm, so eliminate plugs as a possibility.

Oh and check the plug resistance when you have them out especially if the are Champion’s, many say resistance doesn’t matter but by definition high resistance resists electrical flow wasting some energy as heat, the result is less current to the electrodes

 

Edited 18 hours ago by A64Pilot

[slowflyin]

On 5/14/2025 at 10:01 PM, gabez said:

reach out to savvy. great service and very easy to work with 

I did, see my previous post.   

[slowflyin]

1 hour ago, A64Pilot said:

Understood, my main point is to keep looking.

However if the reamer is of the right size and the guide is also correctly sized the reamer won’t do anything, it will only remove metal if the guide is undersized, but I understand if it ain’t broke, don’t fix it.

Try this, exchange the plugs with another cylinder, it’s rare but sometimes you just get a “bad” plug, one that fires correctly when hot but not so much when cold, if it’s a bad plug then the problem will move to the other cylinder. 

This is unlikely, but it costs no money, is easy and does no harm, so eliminate plugs as a possibility.

Oh and check the plug resistance when you have them out especially if the are Champion’s, many say resistance doesn’t matter but by definition high resistance resists electrical flow wasting some energy as heat, the result is less current to the electrodes

 

I agree with the reamer suggestion as a matter of good practice and I may come back to it later.  I could not give them a quick check because I don't have the correct size reamer.  Mcfarland is out of stock of the guided reamers so I chose to put her back together.  I'll have the correct reamer in a couple of weeks and after feeling the guides I'm confident they won't stick open or closed in the interim.

Tried plug swapping.  I did bench test all the plugs (fine wire) under pressure but I did not check resistance.  Good suggestion, thanks!

I'll be doing an inflight ignition test this afternoon.

  

[A64Pilot]

10 minutes ago, slowflyin said:

I agree with the reamer suggestion as a matter of good practice and I may come back to it later.  I could not give them a quick check because I don't have the correct size reamer.  Mcfarland is out of stock of the guided reamers so I chose to put her back together.  I'll have the correct reamer in a couple of weeks and after feeling the guides I'm confident they won't stick open or closed in the interim.

Tried plug swapping.  I did bench test all the plugs (fine wire) under pressure but I did not check resistance.  Good suggestion, thanks!

I'll be doing an inflight ignition test this afternoon.

  

Fine wires I think should be good, I’ve never done it but feel sure you can check resistance without pulling the plugs, would of course have to remove the wire, but I’m afraid that’s honestly not it.

If you swapped them from another cylinder, and the problem reoccurred in the same cylinder, there is an almost zero chance that’s it’s plugs.

If your sure it’s not valves, then the only other likely possibility that jumps out is Injection or ignition, might not hurt to do a flow test and possibly clean that injector, very unlikely I know, but I like to troubleshoot with the free stuff, then the easy stuff before I start spending money myself. If nothing else you eliminate systems. It could be an ignition wire or even cap. If it happens to you again if you can do a mag check looking for increased EGT on the “bad” cylinder, if a plug isn’t firing then of course you won’t get a rise when you turn off that plug in that cylinder but will of course on the others whether the cause be the cap, plug or wire.

I’m afraid that testing when it’s running fine won’t show anything, because it’s not “broke” then.

Call Lycoming’s help desk, they are very knowledgeable and they don’t cost anything.