converting a 65 to a c85 engine

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dfcpac
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converting a 65 to a c85 engine

Post by dfcpac » Thu Sep 15, 2011 08:42

i have a 1971 7aca champ with a a65 and would like to convert it to a c-85 engine. what would be involved? i don;t know which stc paperwork. do you have to change the motor mount and dorsel fin?

thank you
dan carley

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rkittine
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Re: converting a 65 to a c85 engine

Post by rkittine » Thu Sep 15, 2011 12:45

Dan, Do you want to change to a C-85-8 with no accessory case, or a C-85-12 with an accessory case, started etc.

There is both an Aeronca Service Letter that allows the change - I believe that one requires the addition of the larger dorsal fin, and there is at least 1 STC, which I believe does not require the addition of the add on to make the dorsal fin larger.

Although I am not positive, my understanding is that you will need a different engine mount. If you want to use and engine with an accessory case and add a starter I am almost positive of that.

Don, at Don's Dream Machine, can tell you as he does these for a living. Bill Pancake help also.

Ciao - Robert
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com

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rkittine
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Re: converting a 65 to a c85 engine

Post by rkittine » Thu Sep 15, 2011 12:52

Aeronca Service Letter No. 13, covers the conversion of a 7AC to a 7BCM (C-85 engine).
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com

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rkittine
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Re: converting a 65 to a c85 engine

Post by rkittine » Thu Sep 15, 2011 12:58

View the Post on the Buzz Wagner conversion. His son now holds his STCs and I think that he might have had one for a C-85 and not just for the 0-235 Conversion.

Lasher is the other STC that I know about. The www.aeronca.com site is under construction so you can not get all the STC and Service Bulleting information that you can get when it is up.
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
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Paul Agaliotis
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Re: converting a 65 to a c85 engine

Post by Paul Agaliotis » Thu Sep 15, 2011 13:10

Dan,
Check to see how the 7ACA conversion was done. The Service Letters covers conversion of the 7AC, it could be used as supporting data for your conversion.
The same mount will work, but, to remove some of the accessories you will need loosen the mount bolts to let the engine sag a bit.
I don't remember the fuel quantity of the 7ACA, but you really need about 17gal for the C85. Any less and you have a 2hr airplane. Out West it's just not enough fuel.
Paul
Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046

Carl Prather
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Re: converting a 65 to a c85 engine

Post by Carl Prather » Thu Sep 15, 2011 13:41

Dan,

Charlie Lasher also has an STC to convert to a C-85 which is simpler than the service letter. I want to remember that the SL call for a nose tank with a sump or some sort of low point. I think it's a shallow indention downward in the bottom of the tank about the size of computer mouse. Also, C-85 specific baffles are needed. Unless you intend to use a starter or an electrical system, I would think using a the -12 or -8 engine to be not of any significance. I'm paraphrasing here but the Continental Overhaul manual describes the -12 engine as a -8 but with PROVISIONS for a starter and generator. Using them is at the option of the user. Continental made covers for the gen/starter and beyond the the type of magnetos and rear gear set, the operation of either engine is indistinguishable. We have all read about the travails for the -8 vs -12 but my IA say he has never had difficulty with the difference and cites the Continental manuals as proof in any documentation.

Also, a different propeller is on the C-85 for optimum performance. The type certificate tells you what prob to use. Lasher alos a book showing what props can be used in one of his three fine books.

If the the -8 vs -12 thing is a concern, I think that Don's Dreeam machines has a neat -12 to -8 conversion STC. I don't what is entails but if the -8 mags and mag gears are used, there's a huge savings right there if new mag gears are needed.

Good luck

Carl

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rkittine
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Re: converting a 65 to a c85 engine

Post by rkittine » Fri Sep 16, 2011 08:47

Hi Danny,

Give Don a call at Don's Dream Machine - 770-412-8885. He built the 0-200 Part Conversion C-85-12 in my Chief. I have also talked to him about a Rebuild on my C-90-8 or possibly a swap for a C-90-12.

The -8 does not have the bolt holes for the accessory case and according to Don would not be worth the cost to machine a block so that the accessory case can be added. The gears are different and turn in the other direction so you need different mags, gears and tachometer (as the -8 turns in reverse of a -12). All the other parts are the same though, so you can buy a -12 case, mags and gears and rebuild, but Don will do a deal on a -12.

See you are the airport soon.

Ciao - Robert
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com

Roger Anderson
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Re: converting a 65 to a c85 engine

Post by Roger Anderson » Sat Sep 17, 2011 18:50

Paul Agaliotis wrote:Dan,
Check to see how the 7ACA conversion was done. The Service Letters covers conversion of the 7AC, it could be used as supporting data for your conversion.
The same mount will work, but, to remove some of the accessories you will need loosen the mount bolts to let the engine sag a bit.
I don't remember the fuel quantity of the 7ACA, but you really need about 17gal for the C85. Any less and you have a 2hr airplane. Out West it's just not enough fuel.
Paul

I'll second that. We had a 7DC (85hp) with just the original 13 gal. nose tank. It was 2+20 until the engine quit. I once flew a 34 hr round trip flight. 22 fuel stops.

mike newall
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Re: converting a 65 to a c85 engine

Post by mike newall » Thu Sep 29, 2011 11:16

I did such a conversion some years ago.

Used Service letter 13 - very simple.

The tank already had a sump beaten into it with a blunt object !

My prop was a 74" McCauley Met-L prop - IMHO the best for the Champ, leagues ahead of the wood Sensennich club on my first one - horrid prop but looked cute.

To comply with the different harmonics of the new engine, the prop needed shortening by an inch at each tip - local Rabbi helped with that one :lol:

Used existing baffles, a little reworking but nothing major.

C-85 was a -12 and it fitted OK, a little snug but fine. Included a filter at the same time.

Changed the exhaust to a C150 style one with the silencer and better heat exchanger.

All in all, well worth the effort, kept the single tank and I will admit, range was compromised but in England we don't have large distances.

If you are going to do it, don't be tempted to add electrics, it just makes the whole thing too weighty and also very nose heavy. The only exception would be if you can get an STC or 337 to fit a B & C 8 amp alternator just to power a radio/GPS.

I still think that a no electrics C-85 or O-200 produces the best and definitive Champ.

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