Continental A80-8

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Dan Thomas

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Sep 17, 2008
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Ok that makes sense. It would help if it could protect the cylinders when the rainy season hits here on the BC coast.
Even better, don't ground-run that engine. Fly it or leave it alone. Internal engine corrosion is primarily due to water vapor in blowby gases getting into the case and condensing there, reacting over time with the oil and forming acids that eat the engine. Flying it gets the engine and oil hot enough to drive the moisture out the breather tube.

I have found water droplets between the piston and cylinder walls in engines run up before inspection. Found water in the rocker covers, too. Lots of it. And this was in flight school airplanes hangared every night and flown nearly every day.
 

djmcfall

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Oct 18, 2008
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Twin Falls, Idaho
I believe they are two separate additives for two separate purposes. The MMO gets under the rings, and into places in the valve system where pressurized engine oil does not get. The Conti relies on "splash" lubrication for the valve stem for example. The MMO is carried by gasoline, leaving very thin oil in places where fuel gets but oil doesn't.
I have to Chime in to what VB said. I owned an Alon A-2 Aircoupe with a C90-16F. Had issues with sticky exhaust valves. To unstick them I added a little MMO to my crankcase oil, and started adding it to my fuel. Several IA's advised me to, but said they would deny it if anyone asked them about it. No more sticky valves over the next 100 hours and it ran great. Only added to the oil to unstick the valves, after that just added to the fuel. IT WORKS!
 

Ratterrier

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Apr 12, 2020
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I'm Ok flying it I have an electric jacket and gloves, even in December when we get a decent day its quite pleasant to fly for an hour or so even with the open cockpit. The water vapor vapor in the crankcase and valve covers can be considerable in our wet coast climate.
I think I'll run it as a with more pitch and less RPM. With the a80 pistons and the extra compression that gives it should give slightly more power than the a75. Probably not noticeable.
I wondered about leaving that bottom ring off. I imagine it would consume more oil.
One thing I haven't checked yet is if the Stromburg carb jet has been changed or if it has a larger venturi. If it is stock a65 what would be the risks running it as an a75. Will it run lean? or just not develop full power?
 

Victor Bravo

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Take that drain plug out of the Stromberg bowl and see if any water comes out. You can get in there with a very small mirror or one of the newfangled inspection cameras for your phone, and see 100% if that carburetor bowl is corroded and if there's gunk in there.
 

TFF

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Apr 28, 2010
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Memphis, TN
It will run lean if you rev it too much. The family being the same cubic inches, you should have some latitude. You would know if you had CHT/ EGT gauge pretty quick.
 

Dan Thomas

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Sep 17, 2008
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I'm Ok flying it I have an electric jacket and gloves, even in December when we get a decent day its quite pleasant to fly for an hour or so even with the open cockpit. The water vapor vapor in the crankcase and valve covers can be considerable in our wet coast climate.
I think I'll run it as a with more pitch and less RPM. With the a80 pistons and the extra compression that gives it should give slightly more power than the a75. Probably not noticeable.
I wondered about leaving that bottom ring off. I imagine it would consume more oil.
One thing I haven't checked yet is if the Stromburg carb jet has been changed or if it has a larger venturi. If it is stock a65 what would be the risks running it as an a75. Will it run lean? or just not develop full power?
Some time ago on Pilots Of America someone did the calculations to figure out how much water could accumulate in an empty, or mostly-empty, fuel tank over time. It came to nearly nothing. The temperature swings don't expand and contract the air that much. The air, even when saturated, doesn't contain that much moisture, and the water vapor that does get in there doesn't all stay there. An engine crankcase has much less volume than a fuel tank and its mass means that the temperature swings are slower and more limited. There have been plenty of airplanes that have sat for years in a damp climate, and when the engines were opened they were fine. I will repeat: Most corrosion is due to water from combustion blowby gases, and ground-running the engine and putting it away is the worst thing you can do to it.

I had A-80 pistons and cylinders on my A-65 and I ran it as an A-65, at the same redline and prop and all. Didn't have a larger carb for it. It ran OK. Those pistons are really heavy. Leaving off the fifth ring will actually hurt; it prevents a ridge from forming at the bottom of the upper ring travels that starts chipping away at the aluminum piston pin plugs as they past that sharp ridge.

The A-80's Type Certificate was cancelled long ago. I don't know why.
 

challenger_II

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Jul 15, 2009
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Fisher County, Tx. USA
Several "old Fart" A&E's (that dates them!) stated that MMO does wonders for Continental "morning sickness" (exhaust valve sticking, causing shudder and stumble). I tried it in an O-200, and I have never looked back.
They are thinning out quite quickly, but the old Army Air Force, and Air Force (back in the round engine days) swear by MMO. Once upon a time, it had a National Stock Number. So, there must be something to the myth...
 

Wanttaja

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Seattle, WA
Several "old Fart" A&E's (that dates them!) stated that MMO does wonders for Continental "morning sickness" (exhaust valve sticking, causing shudder and stumble). I tried it in an O-200, and I have never looked back.
They are thinning out quite quickly, but the old Army Air Force, and Air Force (back in the round engine days) swear by MMO. Once upon a time, it had a National Stock Number. So, there must be something to the myth...
The man who did the annuals on my Fly Baby when I bought it ~25 years ago was a former Northwest Airlines mechanic, who started his career on DC-6s and Constellations. He instructed me to put MMO in my C-85. I put ~4 ounces in the oil after each oil change, and 4 ounces in the gas tank every 2nd fill.

Touch wood...haven't had any valve problems.

Ron Wanttaja
 

Victor Bravo

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The stuff is not really rocket science, there's no alien technology molecules or Venusian cosmic dust in it. It wasn't invented at Groom Lake, and there's no Mezcal worm extract in it, and you can't put a drop on your tongue and go visit Timothy Leary. A crusty old IA told me it's just a really good lightweight machine oil with a few additives to make it behave a little better in one way or another, some coloring, and a fragrance. But the presence of light machine oil (and whatever additives) in the fuel gets lubrication to places where it doesn't ordinarily get to.
 

Turd Ferguson

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At one time it contained pig lard, I guess to add to the "mystery." And despite the formula changing over the years (predominantly mineral oil), it still retains those magical properties. Amazing no one can duplicate it, or that another brand of mineral oil just won't work. The most amazing thing is outside anecdotal claims, there is no evidence that it does anything. The FAA has documented a couple cases where it contributed to engine fail. Everyone I talk to that is educated in lubrication says put it in your air tools, keep it out of your engine. That's what I do.
 

Pops

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Been using MMO for more than 50 years and never a stuck valve on a Cont, Lyc, VW, autos, motorcycles, farm tractors, etc.
 

challenger_II

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Jul 15, 2009
Messages
201
Location
Fisher County, Tx. USA
The jet/venturi change from a stock A-65 carb, to an A-75 or A-80, was to compensate for the lighter propellers/greater rpm of the A-75/A-80. If you set the engine up with a prop suited to the A-65, and turn it at A-65 book rpm, the stock A-65 carb settings will be fine. Just be aware that you will not be able to run 73 octane fuel with the high-compression pistons. Oh, wait! We can't get 73 octane gas any more! :)

Just keep a close watch on your cht, and oil temp. Those will tell you if the engine isn't happy

I'm Ok flying it I have an electric jacket and gloves, even in December when we get a decent day its quite pleasant to fly for an hour or so even with the open cockpit. The water vapor vapor in the crankcase and valve covers can be considerable in our wet coast climate.
I think I'll run it as a with more pitch and less RPM. With the a80 pistons and the extra compression that gives it should give slightly more power than the a75. Probably not noticeable.
I wondered about leaving that bottom ring off. I imagine it would consume more oil.
One thing I haven't checked yet is if the Stromburg carb jet has been changed or if it has a larger venturi. If it is stock a65 what would be the risks running it as an a75. Will it run lean? or just not develop full power?
 

TFF

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Messages
14,709
Location
Memphis, TN
I think what Marvel has done is survived the original snake oil wars. They make it smell the way it does to keep the original users from figuring out what it was. Today it’s got name recognition and it’s old fashioned enough that no one is going to copy it. Cant be “New” if you copy old.
 

n45bm

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Feb 20, 2019
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Seguin
The stuff is not really rocket science, there's no alien technology molecules or Venusian cosmic dust in it. It wasn't invented at Groom Lake, and there's no Mezcal worm extract in it, and you can't put a drop on your tongue and go visit Timothy Leary. A crusty old IA told me it's just a really good lightweight machine oil with a few additives to make it behave a little better in one way or another, some coloring, and a fragrance. But the presence of light machine oil (and whatever additives) in the fuel gets lubrication to places where it doesn't ordinarily get to.
No mezcal? Bummer. Tequila might make it run "happier", though. Then who'll care about lubrication?
 

Ratterrier

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Apr 12, 2020
Messages
18
If you set the engine up with a prop suited to the A-65, and turn it at A-65 book rpm, the stock A-65 carb settings will be fine.

I ordered a prop 68X47, it should turn somewhere between an A65 and A75. If EGT and CHT are good I can run it at higher RPM if not I'll back it off until it is happy.
and if that doesn't work ....
 
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