Converting a C65 to C85

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Converting a C65 to C85

Unread post by FLYGUYS » Fri Apr 12, 2019 9:08 am

Hi Guys,
Just wanted to find if it is possible to convert a C65 to a C85 and if so what is required ?
Look forward to hearing from someone. :D
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Re: Converting a C65 to C85

Unread post by zig » Fri Apr 19, 2019 9:42 am

Please contact me on 0837771935. I have info and parts which might be of interest to you.
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Re: Converting a C65 to C85

Unread post by FLYGUYS » Mon Apr 22, 2019 11:56 am

Hi Zig,
Thanks for the reply, will give you a shout.
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Re: Converting a C65 to C85

Unread post by Pete » Thu Apr 25, 2019 1:14 pm

FLYGUYS wrote:
Fri Apr 12, 2019 9:08 am
Hi Guys,
Just wanted to find if it is possible to convert a C65 to a C85 and if so what is required ?
Look forward to hearing from someone. :D
Not possible as they are totally different engines. BTW it is an A65 not C65 :smt023
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Re: Converting a C65 to C85

Unread post by FLYGUYS » Sun Apr 28, 2019 2:58 pm

Hi Pete,
Many thanks for your reply.
Regards
Jeff
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Re: Converting a C65 to C85

Unread post by heisan » Mon Apr 29, 2019 10:34 pm

This is a great resource for older Continental engines:

http://www.bowersflybaby.com/tech/fenton.html

Apecifically:

http://www.bowersflybaby.com/tech/fento ... de_to_85hp
A65 Upgrade to 85HP
I am re-building a 1941 J3 with a 65 HP engine. I would like to upgrade it to a 85HP engine with a starter. I would like to find a case and have the engine built. I would possibly also be interested in the 100HP STC so the case would need to be able to use that STC. Three questions. What is the correct case and how can I find drawings for the electrical system and does the electrical system require an STC.

If your plan is to use a lot of the internal parts from the A-65 to build a C-85 be advised that not much is useable. The cam, rods, crank and cylinders are all different than the C-85. You can build up an engine from piece parts starting from just a case, but this is fairly expensive, also. The best bet is to find a complete C-85-12 and work from that as a start. Even a complete, runout engine will yield lots of the small parts which really drive the cost of an overhaul up.

Technically, there is no 100 hp conversion for the C-85. There is an STC to use an O-200 crank, rods and pistons, but the engine is still rated for 85 hp. The O-200 crank conversion is reported to make the C-85 run stronger because O-200 internals are used. However, the C-85 is rated at a lower 2575 rpm than the higher 2750 rpm of the O-200, so the only way to get the C-85 to make 100 hp is to run the rpm illegally high at 2750. The cam of the C-85 is also a bit different, but I don't know what effect that has on engine performance.

The C-85 -12 is the best choice to consider when converting from the A-65. The motor mount configuration is the same between the A-65 and C-85, so the C-85-12 will bolt directly in where an A-65 fits. The O-200 has different motor mounts, so the conversion requires either a completely new motor mount or modifications. The prop from the A-65 can be legally altered to work with the C-85, but, in most cases, is not approved for the O-200.

The electrical system info would need to be obtained from a Piper Cub interest group, such as the Cub Club, www.cubclub.org.

Harry
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Re: Converting a C65 to C85

Unread post by Pete » Tue Apr 30, 2019 6:06 am

heisan wrote:
Mon Apr 29, 2019 10:34 pm
This is a great resource for older Continental engines:

http://www.bowersflybaby.com/tech/fenton.html

Apecifically:

http://www.bowersflybaby.com/tech/fento ... de_to_85hp
A65 Upgrade to 85HP
I am re-building a 1941 J3 with a 65 HP engine. I would like to upgrade it to a 85HP engine with a starter. I would like to find a case and have the engine built. I would possibly also be interested in the 100HP STC so the case would need to be able to use that STC. Three questions. What is the correct case and how can I find drawings for the electrical system and does the electrical system require an STC.

If your plan is to use a lot of the internal parts from the A-65 to build a C-85 be advised that not much is useable. The cam, rods, crank and cylinders are all different than the C-85. You can build up an engine from piece parts starting from just a case, but this is fairly expensive, also. The best bet is to find a complete C-85-12 and work from that as a start. Even a complete, runout engine will yield lots of the small parts which really drive the cost of an overhaul up.

Technically, there is no 100 hp conversion for the C-85. There is an STC to use an O-200 crank, rods and pistons, but the engine is still rated for 85 hp. The O-200 crank conversion is reported to make the C-85 run stronger because O-200 internals are used. However, the C-85 is rated at a lower 2575 rpm than the higher 2750 rpm of the O-200, so the only way to get the C-85 to make 100 hp is to run the rpm illegally high at 2750. The cam of the C-85 is also a bit different, but I don't know what effect that has on engine performance.

The C-85 -12 is the best choice to consider when converting from the A-65. The motor mount configuration is the same between the A-65 and C-85, so the C-85-12 will bolt directly in where an A-65 fits. The O-200 has different motor mounts, so the conversion requires either a completely new motor mount or modifications. The prop from the A-65 can be legally altered to work with the C-85, but, in most cases, is not approved for the O-200.

The electrical system info would need to be obtained from a Piper Cub interest group, such as the Cub Club, www.cubclub.org.

Harry
You can convert anything Justin.. there are many cases of guys changing in to girls and vice versa.. :shock: 8-[ but as Harry Fenton says "The best bet is to find a complete C-85-12 and work from that as a start."

I would be rather anxious flying behind a bored out A65 lightweight crankcase with thru bolt holes that were drilled oversize to accommodate a C85 crank and cylinders!

Been around these little Contis for years and my advise is like Harrys, keep it simple and safe.. :smt023

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Re: Converting a C65 to C85

Unread post by heisan » Tue Apr 30, 2019 9:51 am

Yup - I was just posting it for additional information. If you read further, it is possible to get C-85 power levels from a A-65 with minimal modifications, and 'acceptable' (whatever that means) reliability.

But as always, unless you enjoy experimenting it is best to keep things standard.
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