c-85

[dannys]

Hi all,

I am in the process of restoring a 1946 BC-12D that has a 85hp continental.

I am going to have the engine completely overhauled and would like to know if you can modify the engine without getting a field approval and get more power out of it.
I originally was going to put a 100hp cont on but after talking to my maintenence POI about the new field approval process he talked me out of that saying it would be very difficult to get a field approval in todays environment.
any suggestions??
danny

[jgerard]

I think I have seen an STC for the 0-200 in the BC12D with out the gross wight increase.

OR

If you're not worried about paperwork build a rat motor and hang on!

Jason

[NY86]

Get an STC to install the O200 rods, pistons and crank in the C85. When you're done, it's still a C85 so no approval is necessary other than the engine STC. YOu get an increase in displacement and compression. It'll run with an O200 any day orf the week!

Don's Dream Machines or Aircraft Specialties Services sells the STC.

[dannys]

how does the case hold up with the increased h/p
is it more susceptible to cracks?
does reliabilitie go down??
do you use the same engine mount?
danny

[jgerard]

It would be a good idea to have the case machined and install the 0-200 case through bolts.

Jason
N43643

[NY86]

I believe it is not possible to machine an early case to accept the center through bolts. Later cases were made the same as O-200 cases and have the through bolts. Also, all C90-14 and -16 cases have the through bolts, but one (I forget which) also has the O200 Lord mounts. The reason it cannot be done is the early cases have an oil gallery running through the area you need to machine out.

If you do not go to Lord mounts the engine mount stays the same. Bolt an O-200 to a mount intended for the C-85 style and the engine shifts 3/8 to 1/2 inch forward.

That said, I do not feel there is a significant reliability issue. The reason I say that is that EVERY C-series I've seen that had cracks in the center main bearing support had suffered a prop strike between the last overhaul and the moment of discovery. Ergo, I believe that prop strikes are the big problem. So run a wooden prop...

BTW, they (the ones with the cracks) were all running fine, too, just making metal in the oil.

YMMV,

[Frank DeBartolo]

Originally posted by jgerard
I think I have seen an STC for the 0-200 in the BC12D with out the gross wight increase.

OR

If you're not worried about paperwork build a rat motor and hang on!

Jason

[Frank DeBartolo]

Originally posted by jgerard
I think I have seen an STC for the 0-200 in the BC12D with out the gross wight increase.

OR

If you're not worried about paperwork build a rat motor and hang on!

Jason

What's a rat motor?

Frank DeBartolo
N43684