Lycoming cam wear power loss

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Dan Thomas

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Actually, Lycoming recommends 1000-1200 "when possible" to prevent lead fouling.
We didn't have fouling issues, either, though we didn't have long taxis to do. Leaning it way back limits the fouling, and installing UREM37BY plugs in any engine approved for them pretty much eliminates it altogether.
 

BBerson

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My Cherokee cam looked like that at TBO. Bought a new cam ($400 1979) and didn't notice any power difference.
 

dog

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Actually, Lycoming recommends 1000-1200 "when possible" to prevent lead fouling.


Nope, it's best to not move the prop. Moving it without actually running can scrape off any oil film that's on the surfaces.
Nope,it moves the small contact patch that is alowing galvanic corrosion to develope and isnt enough force to "scrape" off the oil film.
 

BJC

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I have heard that the best and simplest way of
keeping an engine good is to pull the prop through one cylinder every time you go by.
Nope, it's best to not move the prop. Moving it without actually running can scrape off any oil film that's on the surfaces.
Nope,it moves the small contact patch that is alowing galvanic corrosion to develope and isnt enough force to "scrape" off the oil film.
I'm not an engine guy, so I have asked three different Lycoming tech reps about pulling the prop through prior to starting, and all said the same thing: don't do it. That leads me to two questions:

Is there something different in dog's assertion verses pulling a prop through before starting?

Is there a citation for dog's assertion?

Thanks,


BJC
 

Dan Thomas

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Is there something different in dog's assertion verses pulling a prop through before starting?

Is there a citation for dog's assertion?
Pulling the prop though before start isn't the same as pulling it through and leaving it sit like that. There is no oil pressure generated at such a low RPM to provide any more oil to anything, and whatever oil is there just gets scraped off the cylinders by the rings. If there has been some corrosion between the cam and lifter, that spot just gets moved elsewhere to make a new spot of corrosion. And if the ambient air is really humid, you just sucked a fresh charge of it into one or more cylinders, where that moisture will condense when things get cool, and add to the corrosion problems.

The Lycoming techs' responses may be driven by the risk of the engine firing and maiming or killing someone.

The Lycoming Key Reprints document offers good advice: http://www.alfako.be/SAFETY DOCS/lycoming---flyer_key_reprints.pdf

On page 96 there is discussion of cam and lifter corrosion. Starting on page 65 is a bunch more stuff on corrosion in infrequently-flown engines, and some OWTs are addressed along with sparkplug fouling and so on. One thing they do say there: If the engine can't be flown, then merely pull it through by hand or briefly turn the engine with the starter to coat the critical parts with oil. Therefore, we have a conflict between this Lycoming document and that of the Lycoming people you asked about it. If it was my engine I would leave it alone. The difference between pulling it though by hand and using the starter is that the starter will rotate it fast enough and long enough to bring some fresh oil into the system, but the RPM will be much too low to fling any onto the cam and lifters. Using the starter also depletes the battery, and leaving it partially discharged will sulfate it and ruin it. My advice is to fly it or leave it alone.
 

PiperCruisin

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My A&P was recommending filling the engine with oil if you were going to let it sit for too long. Never seen it done. How many planes are sitting out there idle for years?
 

TFF

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When storing engines not factory picked I flip them upside down in a cradle and put about 10q of oil and submerge the cam. It gets some oil on the skirts. Fill up the cylinders with oil from bottom sparkplugs.
Pulling the engine through is probably more of a safety concern, your old Starduster owner had a Rotax 912 start while pulling through. Did not know it was even possible, but a P lead had broken. Turning the prop just cleans off the lifter and lobe. That is what the cam guard does, which is make more oil cling to the cam and lifters to protect them. The H2AD engine had Ford lifters in it originally which were a smaller diameter, and they would go through cams like candy. Solution was to design mushroom lifters like the regular Lycomings but that requires splitting the engine. AD on an engine name is never a good idea. There is an STC to put a roller cam in it. There is also a cam mod STC that plugs the ends of the cam so it becomes an oil gallery and on the lobe before it ramps up a small hole is machined in. Oil oils the lobe before it hits the lifter much more aggressively. Relatively cheap mod.
 

Dana

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Lycoming has a recommended procedure to prepare engines for storage. It involves changing the oil and putting in preservative oil, running it until it's up to temp and then not turning the crankshaft after shutting down, spraying oil into the cylinders, putting in desiccant plugs, and sealing all other openings into the engine.

Since you mention the lifters, Tom... do the solid lifter Lycomings (O-235 and 290-D) cams fare the same as the ones with hydraulic lifters?
 

Dan Thomas

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Lycoming has a recommended procedure to prepare engines for storage. It involves changing the oil and putting in preservative oil, running it until it's up to temp and then not turning the crankshaft after shutting down, spraying oil into the cylinders, putting in desiccant plugs, and sealing all other openings into the engine.
Here's that Lycoming document: https://www.lycoming.com/sites/default/files/Engine Preservation for Active and Stored Aircraft.pdf

An excerpt:

Pulling engines through by hand when the aircraft is not run or flown for a week or so is not recommended. Pulling the engine through by hand prior to start or to minimize rust and corrosion does more harm than good. The cylinder walls, piston, rings, cam and cam follower only receive splash and vapor lubrication. When the prop is pulled through by hand, the rings wipe oil from cylinder walls. The cam load created by the valve train wipes oil off the cam and followers. After two or three times of pulling the engine through by hand without engine starts, the cylinders, cam and followers are left without a proper oil film. Starting engines without proper lubrication can cause scuffing and scoring of parts resulting in excessive wear.

That's for engines with normal oil in them, not the storage oil. With the storage oil, they say this:

Reinstall spark plugs and do not turn crankshaft after cylinders have been sprayed.
 
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TFF

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There is not a difference in quality of the lifters. The issue that a 290 has is age. Put a number on when the last time the guts were looked at on a 290. Replaced with new? Same with a 235. Almost every one has been in service a long time. The engines are good, but good chance they are 20-40 years old overhauls. With the solid cam you do have a window into health. Valve adjustment. They all need minor adjustments, but if you got one that needs more and more, it’s probably on the way out.

Mine, I saw the cam. My engine is a mash of great parts mixed with parts someone thought were great but not. My cam is early stage pitting. It was “rebuilt” and had 98 hours when it nosed over. Then it sat on a stand for 20 years. I got my little hands on it and it would not turn. What happened was the lifters and valves gummed up would not let the engine spin. Once it did there was no compression because all the valves were open. Im glad I cracked it open. I did not rework the cam. I’m going to see how it goes. Nothing worn but I imagine it’s probably what a mid time aged engine looks like.
 

BBerson

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I don't know anyone that pickles an engine before or after 30 days. The best solution would be to inject a high pressure oil fog into the cold engine. Crank it three times by hand (stand clear). Then refog it a bit. The rings don't scrape tight without cylinder pressure. If you don't move it every once in a while the rings will rust into one spot.
 

Dan Thomas

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I don't know anyone that pickles an engine before or after 30 days. The best solution would be to inject a high pressure oil fog into the cold engine. Crank it three times by hand (stand clear). Then refog it a bit. The rings don't scrape tight without cylinder pressure. If you don't move it every once in a while the rings will rust into one spot.
I don't know anyone that does the 30-day thing either. Some floatplane guys don't convert to wheels or skis in the winter, so they'll pickle the engine.

Rings won't rust into one spot. Never seen that other than in engines that had water get into them and left like that. The bigger damage comes when owners ground-run the airplane and put it away; water vapor in the blowby gases condenses in the case and in some funny places like the interface between the piston and cylinder. Now, take aluminum and steel, put them together with a film of oil, and add some water. The dissimilar metals and water start galvanic corrosion, and the oil mixes with the water and forms acids. The acids do serious damage. I have taken the cylinders off an engine that has just been run up (from cold) for oil change and differential compression testing. The filter shows aluminum chips, maybe, a sign that the piston pin plugs are being shaved by the lower ring ridge in the cylinder, or maybe the compressions show a leaking valve. Anyway, there are water droplets between the piston and cylinder and sometimes quite a lot of water in the rocker boxes. This was in engines at a flight school, run hard almost every day. Hangared every night.

Fly it or leave it alone. Airplanes have sat for years, often outside, undisturbed, and the engines are still OK inside.
 

TFF

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I started up an engine that had not run for four years parked on the ramp. A friend bought it and wanted to here it run. I hand turned to over by hand about ten times until I knew it had compression I could feel, or I was not going to start it. Jumper pack and three blades and away it went. I have had a work engine not pickled but plugged up have no issues after 6 years, but I did have another one we bought that was stored like trash and rusted up the cylinders. The crankcase was clean.
 

AdrianS

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It's not a Lycoming, but :
my injected 2-stroke outboard motor has a 'winterise' option where it warms up then cuts the ignition & fuel and injects a bunch of oil as the engine is stopping.

Always thought that was a clever idea.
 

dog

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I'm not an engine guy, so I have asked three different Lycoming tech reps about pulling the prop through prior to starting, and all said the same thing: don't do it. That leads me to two questions:

Is there something different in dog's assertion verses pulling a prop through before starting?

Is there a citation for dog's assertion?

Thanks,


BJC
No citation,going from memory of something
I read and accepted,as it seems to fit with the
accounts of engines that sit ,having the cams
rot on the lobes but not on the journals.
A possible agravivating factor could be zink or
other metals in used oil contibuting to galvanic
corrosion.
And an engine that is already making metal is
going to deffinitly corode while sitting.
Cast cam,wet oil with metal,steel lifters,volt meter just might show a tiny current.
Living in the north east,corrosion of all types is
a constant worry,and with so many freeze thaw
cycles conditions for condensation are often
perfect.
So I am trying to understand all of the other variables and complications,of which there isnt
much of a consensus.
Just the sub topic of water vapor is a rabbit hole full of counterintuitive behaviors.
 

Dan Thomas

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No citation,going from memory of something
I read and accepted,as it seems to fit with the
accounts of engines that sit ,having the cams
rot on the lobes but not on the journals.
A possible agravivating factor could be zink or
other metals in used oil contibuting to galvanic
corrosion.
And an engine that is already making metal is
going to deffinitly corode while sitting.
Cast cam,wet oil with metal,steel lifters,volt meter just might show a tiny current.
Living in the north east,corrosion of all types is
a constant worry,and with so many freeze thaw
cycles conditions for condensation are often
perfect.
So I am trying to understand all of the other variables and complications,of which there isnt
much of a consensus.
Just the sub topic of water vapor is a rabbit hole full of counterintuitive behaviors.
Over onPOA someone did the calculations for condensation in an empty fuel tank. Even with saturated air and extreme temperature swings it takes a long time for any measurable moisture to accumulate, and that's assuming that ALL the moisture going in stays in, which is impossible.

Now, a crankcase, with the crank and cam and rods and everything in it, has far less volume than a tank. It's miniscule. Engine internal corrosion is primarily from blowby when the engine is warming up. The only practical way to get it out is to get it hot enoigh for long enough, meaning it has to fly.
 

dog

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Over onPOA someone did the calculations for condensation in an empty fuel tank. Even with saturated air and extreme temperature swings it takes a long time for any measurable moisture to accumulate, and that's assuming that ALL the moisture going in stays in, which is impossible.

Now, a crankcase, with the crank and cam and rods and everything in it, has far less volume than a tank. It's miniscule. Engine internal corrosion is primarily from blowby when the engine is warming up. The only practical way to get it out is to get it hot enoigh for long enough, meaning it has to fly.
Odd,as in your post # 52 above you describe water in the rocker boxes ,in airplanes flown hard everyday.Which would presumably drain
back onto the cam and lifters?yes?
What am I missing here?
 

TFF

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Cars have some form of positive crank case ventilation since the 60s. It makes the rings work better so there is less blow by, the engine consumes some of the bad vapors, the oil stays cleaner longer; lots of wins. Except, standard auto pcv needs part throttle vacuum to work, so you have to hook an airplane up like a race car to the exhaust. The bad part comes if the one way valve carbons up and sucks all the oil out. It does it fast. You just introduced something that can help but hurt too. You have to keep on top of it.
For ground, You can make up desiccant packs. You have a hose that slips on the breather and oil fill running to a big pack and try to suck moisture out while parked. The minute you stop an engine, relatively cool air going up the breather tube makes it “rain” in the engine. Pretty much sticks wherever it was last.
 

BBerson

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If you starter crank an engine occasionally with no ignition or no fuel it should splash lubricate the cam without introducing blow by moisture.
 

Dan Thomas

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Odd,as in your post # 52 above you describe water in the rocker boxes ,in airplanes flown hard everyday.Which would presumably drain
back onto the cam and lifters?yes?
What am I missing here?
You are missing what I said about this being airplanes that had just been pulled out and run up prior to inspection and oil change? That's when most water gets into a crankcase: when it's being run up from ambient temperatures. Clearances are larger so blowby is much worse.

I had said:

I have taken the cylinders off an engine that has just been run up (from cold) for oil change and differential compression testing. The filter shows aluminum chips, maybe, a sign that the piston pin plugs are being shaved by the lower ring ridge in the cylinder, or maybe the compressions show a leaking valve. Anyway, there are water droplets between the piston and cylinder and sometimes quite a lot of water in the rocker boxes. This was in engines at a flight school, run hard almost every day. Hangared every night.

I mentioned that "they were run hard almost every day and hangared every night" so that nobody could say that it was condensation from the atmosphere in the engine. I have taken cylinders off airplanes that have come back from long flights and found no water anywhere at all.

Clear now?
 
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