C-85 vs C-90

[n6346m]

I am considering an engine upgrade for my L2-B. Now that the conversion STC is available, I need to decide which engine to use. First, I can't afford a Don's dream machine engine that everyone seems to rave about. I probably will have to find a runout engine here in Alaska and overhaul it myself.
I hear that a C-90 is the best engine to use because of the prop availabilities and the most desireable power curve for this particular application. The O-200 is more readily available but is heavier. I do not plan to use a starter or generator so that is not a factor.
C-85's seem to be more plentiful than the C-90. Can the C-85 be converted to a C-90?
Finally, if the future allows I may want to put floats on it.
Any suggestions out there?
Bob

[astjp2]

Re: C-85 vs C-90

Bob, the Don's conversion is basically converting the 85 rotating assembly to C-90/O-200. Its 350.00 for the STC to put the O-200 crank in the 85 case. You will need to run the 85 cam to keep it legal but that is what you are looking at. If you have any more questions, give me a shout. Tim

[Dano"T"]

Re: C-85 vs C-90

A C90 is better...I have a C85 powered BC12D and a C90 Powererd BC12D....The C85 cannot be converted to a C90....If you can't afford a Don's dream...then go with the C90....if you can't find one...go O200 for better parts availability.

[barnstmr]

Re: C-85 vs C-90

Of all the available options on the STC, the C90 will be the best in my opinion. But, the parts are not as plentiful, so cost may be higher.

Here is the best part about the C90...
95 hp at 2625 RPM (takeoff 5 minutes)
90 hp at 2475 RPM (max. continuous)

and for the C85...
85 hp at 2575 RPM (continuous)

and for the O-200....
100 hp at 2750 RPM (Takeoff 5 minutes only)
93 hp at 2530 RPM (Maximum Continuous)

Making the same or greater power at slower RPM allows the prop to be more efficient.

[Guest]

Re: C-85 vs C-90

Which parts are you guys thinking of that are not so available for a C-90?

I have a C-90 and can only think of is the that is different is cam and lifters. Otherwise I think all parts are same as O-200.

Dave

[astjp2]

Re: C-85 vs C-90

Which parts are you guys thinking of that are not so available for a C-90?

I have a C-90 and can only think of is the that is different is cam and lifters. Otherwise I think all parts are same as O-200.

Dave

Dave, the case is different between the older C-90 and the O-200, there is a difference on the through bolts. Tim

[Guest]

Re: C-85 vs C-90

Thanks Tim,

Now that you mention that I recall having to measure something to get the correct thrust bearings and seal or something like that.

Divco did the case and supplied the bolts, they lost mine, worked out good for me .

Dave

[Ragwing nut]

Re: C-85 vs C-90

I am considering an engine upgrade for my L2-B. Now that the conversion STC is available, I need to decide which engine to use. First, I can't afford a Don's dream machine engine that everyone seems to rave about. I probably will have to find a runout engine here in Alaska and overhaul it myself.
I hear that a C-90 is the best engine to use because of the prop availabilities and the most desireable power curve for this particular application. The O-200 is more readily available but is heavier. I do not plan to use a starter or generator so that is not a factor.
C-85's seem to be more plentiful than the C-90. Can the C-85 be converted to a C-90?
Finally, if the future allows I may want to put floats on it.
Any suggestions out there?
Bob

If you don't plan to use a strater or generator find an C85-8 and stroke it. C90-8 engines are very rare. The stroker STC puts the crank, rods, and pistons of an 90/200 into the 85. The STC can be bought from A/C Specialties

[NY86]

Re: C-85 vs C-90

The C-85 CAN be converted to a C90. See the appropriate Continental Service bulletin.
Forget about the 95 HP takeoff limit. The only way you'll ever see that is if you have an adjustable prop. Still, the best engine...

[Ragwing nut]

Re: C-85 vs C-90

The C-85 CAN be converted to a C90. See the appropriate Continental Service bulletin.
Forget about the 95 HP takeoff limit. The only way you'll ever see that is if you have an adjustable prop. Still, the best engine...

No it can not. Just because the bulletin allows it, does mean physically it can. Depending on the 85 case, the larger diameter tappet bodies of a 90/o200 will not clear the main web casting. It is a hit or miss thing.

[astjp2]

Re: C-85 vs C-90

I have read the service bulletin, you can get the case machined for the larger tappet bodies...the main difference is the through bolts.

http://www.aeronca.org/ContinentalSB-M49-17.pdf

It was an issue on the early C-90 cases also...Tim

[Ragwing nut]

Re: C-85 vs C-90

I have read the service bulletin, you can get the case machined for the larger tappet bodies...the main difference is the through bolts.

http://www.aeronca.org/ContinentalSB-M49-17.pdf

It was an issue on the early C-90 cases also...Tim

That I have not read before, learn something new everyday.

[NY86]

Re: C-85 vs C-90

...the main difference is the through bolts.

Actually, the through bolts didn't come into being until the O200. Prior to that, all C90 cases had studs just like the C85 and everything earlier. When the O200 was intrOduced, all new cases from that time forward had through bolts even if they were destined for the "lesser" engines.

[Ragwing nut]

Re: C-85 vs C-90

Actually, the through bolts didn't come into being until the O200. Prior to that, all C90 cases had studs just like the C85 and everything earlier. When the O200 was intrOduced, all new cases from that time forward had through bolts even if they were destined for the "lesser" engines.

I beleive the C-90-14 or -16 has floating through bolts.