Data time - Burned exhaust valves

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Mtns2Skies

Final Approach
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Mtns2Skies
Here's my last instrument training flight engine monitor readout in the 180... I'm thinking I've got a couple burned exhaust valves on cyl's 2 & 3, and maybe 1. What say you PoA? Cold day of flying, full rich mixture at all times.

Other than the EGT, no other symptoms or issues, oil consumption is low, oil analysis is good, power is good.

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Whatcha lookin at? Have you poked your bore scope in there yet? I'm certainly no expert, just trying to learn.
 
Are you showing that, while full rich and at cruise power, you have EGT spreads over 300 degrees? Full rich you have EGTs over 1600?
 
Carbureted engine, new(ish) champion sparkplugs (switching to tempest at annual). Also getting a new exhaust at annual.
 
What did it do previously under similar conditions?
 
mondtster said:
What did it do previously under similar conditions?
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Not really sure, the engine monitor is new as of last summer. This is the first time I've flown in this cold of temps with it. In warmer temps, while there's still a spread I haven't seen the EGT get over 1600F. I'm hoping this is just me being a hypochondriac brought on by a new engine monitor.
 
Mtns2Skies said:
Not really sure, the engine monitor is new as of last summer. This is the first time I've flown in this cold of temps with it. In warmer temps, while there's still a spread I haven't seen the EGT get over 1600F. I'm hoping this is just me being a hypochondriac brought on by a new engine monitor.
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That’s what I figured. This is why I don’t like engine monitors, nobody knows what they should be seeing but they sure get wound up about it anyway.

Unless there is obvious proof that the valves are burnt I’d just motor on. A spread of EGTs on what has to be one of the most poorly designed induction systems shouldn’t come as a surprise. The higher temps are likely due to the cold weather we’re having in the Midwest right now (leaner than you’re used to).
 
Tune up your valve geometry so the rockers contact the valve squarely. Until you do that you’ll have valve guides wear and that leads to valves not seating properly. It’s common in big bore Continentals.

How’s you leaning authority in the cold wether? Still able to lean 100* before you get a stumble? You may just be running too lean. Another common big Continental struggle.
 
Stewartb said:
Tune up your valve geometry so the rockers contact the valve squarely. Until you do that you’ll have valve guides wear and that leads to valves not seating properly. It’s common in big bore Continentals.

How’s you leaning authority in the cold wether? Still able to lean 100* before you get a stumble? You may just be running too lean. Another common big Continental struggle.
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I'll bring this up to my A&P. Annual is just a few weeks out. I'll check leaning on my next flight, but I'm thinking you may be right.
 
When you say cold, how cold? Dense air, more fuel...
 
If you suspect a burned valve, have you done compression check to see if you do have a leak?
 
May I suggest Mike Busch's book on engines?. I'm kinda thrilled I've read it. Realized I've been doing a few things right, and wrong over the years. Sure has busted a few old hangar pilots tales.

I read how to read engine monitor results. I have one on the shelf, and it's going in the plane asap now that I've read his book.
 
Sounds like a perfectly average Continental carb'd engine. Engine monitor in such a coarsely inducted engine? Meh.

Conti cylinders are throwaway anyways (but you knew that). Just my biased 2 pesos. Awesome plane though. A Lycoming mill would make it better.:D
 
hindsight2020 said:
Sounds like a perfectly average Continental carb'd engine. Engine monitor in such a coarsely inducted engine? Meh.

Conti cylinders are throwaway anyways (but you knew that). Just my biased 2 pesos. Awesome plane though. A Lycoming mill would make it better.:D
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Just here to troll?
 
M2S, my own big Continental had temps all over the place until the jet was opened up to allow more fuel flow. Now? All temps are better regardless of mixture setting. It was like magic. My temps are essentially flat, like fuel injection flat. Do pay attention to your leaning authority. You may be operating at peak or lean of it. Timing being off can contribute to irregular temps, too. And you should be inspecting the intake rubbers every time the cowl is off. Check them carefully, especially at the Y pipe. If you have thumb turn clamps? Get a 5/16 or 3/8" nut driver and cut a slot in it. You can put some oomph to those thumb turns with a properly modified tool.

Here's a great old article about the 0-470. Kas Thomas used to have some pretty good 0-470 advice in TBO Adviser, too. I miss that guy's writing.
https://www.avweb.com/news/reviews/182885-1.html
 
I'll just leave this here

There is some great commentary about the Oh470 in the questions at the end about leaning.

Then I noticed I can Google oh470 and Mike Busch and get a crap ton of info about how that engine really runs.
 
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Stewartb said:
Ya, but if he wrote it there's a good chance he got it wrong. ;)
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Ya know, Mike Busch knows a lot of stuff, and I believe most of what he writes, but his CHT-based leaning procedure in that article sucks. He should listen to his friends and use EGT.
 
JOOC, what in that data leads you to believe you have toasted some valves?
 
Seems this comes up every few months. The actual number on an egt means squat. All it tells you is how far from the exhaust port your probe is. Every manufacturer has a range that they should be in, Closer you get a higher number,faster response, and faster probe wear. Farther you get a lower number, slower response and longer life. The importaint thing is they are all the same distance from the flange. What matters is temp spread between cyls and large changes from what you normally see.
 
I flew yesterday when it was 45*F out (woohoo) and the engine was happy as could be. Temps were low across the board. Clearly my carb is set too lean. Score for the engine monitor for catching is (kinda). :)
 
Regardless, get the $40 borescope camera on Amazon before your annual and take pics of all of the exhaust valves. That will tell you some much more useful data than your engine monitor currently is ;-)
 
Stewartb said:
M2S, my own big Continental had temps all over the place until the jet was opened up to allow more fuel flow. Now? All temps are better regardless of mixture setting. It was like magic. My temps are essentially flat, like fuel injection flat. Do pay attention to your leaning authority. You may be operating at peak or lean of it. Timing being off can contribute to irregular temps, too. And you should be inspecting the intake rubbers every time the cowl is off. Check them carefully, especially at the Y pipe. If you have thumb turn clamps? Get a 5/16 or 3/8" nut driver and cut a slot in it. You can put some oomph to those thumb turns with a properly modified tool.

Here's a great old article about the 0-470. Kas Thomas used to have some pretty good 0-470 advice in TBO Adviser, too. I miss that guy's writing.
https://www.avweb.com/news/reviews/182885-1.html
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Just following up with this @Stewartb you were exactly right. At annual last month I got the carb turned richer (waaay richer, my A&P found it far far too lean) and now my temps are perfect and the engine is way happier. The EGT differential went from 300 to 30-70 depending on power setting and OAT. What a world of difference it made for 0.5 hours of shop time! Thanks for the suggestion, it made diagnosis way easier!
 
Mtns2Skies said:
Went from 12gph to 12.8gph. Measured via flying and fueling up, I don't have a fuel totalizer.
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Mtns2Skies said:
Just following up with this @Stewartb you were exactly right. At annual last month I got the carb turned richer (waaay richer, my A&P found it far far too lean) and now my temps are perfect and the engine is way happier. The EGT differential went from 300 to 30-70 depending on power setting and OAT. What a world of difference it made for 0.5 hours of shop time! Thanks for the suggestion, it made diagnosis way easier!
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Move from Colorado to Wisconsin responsible for that situation?
 
GRG55 said:
Move from Colorado to Wisconsin responsible for that situation?
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Possible, more likely is the install of the JPI allowing me to diagnose the problem. Plane was originally based in Detroit, so similar altitude as here, just less instrumentation.
 
Mtns2Skies said:
Possible, more likely is the install of the JPI allowing me to diagnose the problem. Plane was originally based in Detroit, so similar altitude as here, just less instrumentation.
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I just recall I had to have the fuel injection idle mixtures leaned out on my Aztec when I bought it in Missouri and moved it to the mountain country.
Regardless, the engine monitor is, imo, indispensable. I'd trade any number of gyro replacement glass instruments for an engine monitor any day.
 
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