Continental A80-8

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Ratterrier

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Hi, So I picked up a small Continental that I am wanting to power my small biplane. I had thought I bought an A65, But found after pulling a cylinder discovered it was newly converted to an A80 with .015 over pistons. Now I am posed with the conundrum of what to do with it. The pistons rods and exhaust valves are new never ran. From what I understand the a80's had issues with heat dissipation and putting stress on the case. If I set this up and ran it as a A65 2300 RPM 2150 and proped it acordingly The compression would still be higher (6.3 for the A65) and 7.55 for the A80 pistons. Could I get better longevity and reliability?
The other thing I am up against is finding Mags I've been looking for a Bendix S4RN-21 seem to be scarcer then hens teeth If anyone has a core they'd part with..... Tkanks
 

Kyle Boatright

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Why not convert it to an A-75? Same compression as the -65, but higher allowable RPM and higher HP. There is/are/was/were no issues with the A-75.
 

Ratterrier

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Yes I'd be happy with the A75 , just very reluctant to buy new pistons and rings. Some times wish I was wealthy.
 

Pops

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Yes I'd be happy with the A75 , just very reluctant to buy new pistons and rings. Some times wish I was wealthy.
I'm leaving for a few days and when I get back home I'll look and see if I have a set of A-75 pistons, I may, or my not. I'll let you know. Almost sure I have a set of 80 hp pistons, but if I remember correctly, might have a set of A-75's.
 

Ratterrier

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Thanks Pops. I should probably drop it to 75. I would save a couple lbs as well. The ones for the 80 are quite heavy. The five rings were a total surprise to me.
 

Victor Bravo

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If you run it as an A-75, you will have no problems with it. Take the time to balance everything within the reciprocating mass... rods, rod caps, pistons, rockers, valves, etc... all of it.

While you have the cylinders off of it, put the new better pushrod seals on the pushrod tubes, trust me. The Continental pushrod seal rubbers and those [email protected]@%^&#G hog ring clamps leak.

Put the later O-200 or O-300 oil breather fitting in it, this one sticks further into the crankcase than the others. Well worth it.

Make sure your cowl has the little scoop under the crankshaft, and make sure it puts high pressure air into a duct that is sealed so the air MUST run along the bottom of the engine crankcase. There is a cheap looking sheet metal baffle that goes between the intake spider and the bottom of the spider mounting bosses. Make sure this baffle is there and seals well against the sides of the engine, between the cylinder bulges in the case casting, etc. This baffle contains the air form the front intake and duct, and forces that cool air to run along the bottom of your crankcase. This is the oil cooler on the A series Continentals, and it works. All you have to do is make sure the air cannot leak out the sides, and is forced to bathe the lower crankcase and oil return pathway in cooling air.

Run Marvel Mystery Oil in the gasoline, at about 1/2 of the ratio recommended on the bottle. You will clean your spark plugs a little more often but you will not be replacing rings, valves, and rockers. I'd say it's a very good deal money-wise.
 

Ratterrier

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Thanks Victor Bravo, some very good advice. Good cowling is a must in a slow biplane , and the importance getting the air to the bottom of the crankcase I hadn't considered.
 

aviatorbell

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I have an A-65-8F that i bumped up to 8:1 using the Lycon NFS pistons. They are slightly heavier than the 65/75 pistons but are a balanced set. They run very smoothly at 2600 rpm. I think they were about $160 each when I bought them in 2017. They use stock continental rings, 2 compression and one oil ring. Just another option.
 

Ratterrier

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I’d run it just like it is. A-80’s run just fine!!

But would you expect it to have the longevity and reliability of the a-65 or a-75 that's the question. I had thought I had bought an A-65 and wanted the 65's reliability. I'm just concerned I might lose that with the 80.
 

TFF

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Cam Guard makes oil stick to the cam. Marvel washes sludge off the inside and hopefully out during an oil change. Nothing wrong with marvel but it was really a bigger deal before ashless dispersant oil.

How reliable does it need to be? Will you fly 500 hrs, 1000, 2000? Is it really a hand grenade? I want to fly 2000 on my plane but I probably will not reach that without someone paying the fuel bill. Run with a 65 or 75 prop and that’s all you will use if you manage the RPM.
 

Victor Bravo

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Is Marvel Mystery Oil as good as or better than Camgard?
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.
 

TFF

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You can put Marvel in oil or gas. I put it in my Alfa fuel when I remember. Most airplane people around here put it in the oil.
 

Ratterrier

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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.
 

Victor Bravo

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Your cylinders can be protected against corrosion by using desiccant plugs in the exhaust, and covering over the carburetor air intake, and desiccant plugs in the crankcase breather. That corrosion is a separate problem than poor upper cylinder lubrication, and requires a separate solution. The oil sliding off the cam lobes is yet another problem worth solving, and requires another solution (Cam Guard or whatever).

It's all several little things that add up to an engine that runs better for a longer period of time.
 

robertbrown

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An old timer who knew those engines from when they were new said that the A-80's were bad about burning holes in the pistons. They were running 73 octane fuel or less in those days so I would suspect that they had preignition and that you wouldn't get it with today's fuel. I'd be tempted to try the A-80 pistons since you already have them.
 

TFF

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You could always see how thick the crowns are. If they are thicker than A-65 pistons, chuck them in a lathe and match the thickness, then you would have “A-65” pistons. I might even leave the skirt rings off too if I had two compression and an oil ring at the top.
 
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