National Aeronca Association Bulletin Board

Is it Possible to use a C-90 case inplace of a C-85. I have recallections of a Service Bulletin that said you could change the designation of an engine by changing the internal parts, but haven't been able to find it.

i.e. if you take a C-90 case, but use 85 crank, cam, pistons, cylinders, etc.. It becomes a C-85

Anybody got some insight?

nkh

thanks Joe.

Hi: The C-85-8 and C-90-8 are the same case. The 85 and 90- 12s are the same case, at least according to my parts listings. Ron

i Have the service letters and you can get them for continental

I did some digging around and got a little more insight into this topic.
Apparently the cases are the same, as in they both come from the same casting molds. But they are MACHINED differently. A C90 will have the tappet (or lifter body if you will) bosses cut farther into the side of the case to clear the lobes of the cam. Further, the lifter body is shorter in a C90 than that of a C85.

In the front of the overhaul manual and on the Continental Service Bulletins, they both mention Case swapping. All they state is you can make a C90 into a C85 but you can not go the other direction. It's clear why they say that now. Putting a C90 cam into a C85 case would be a great way to make metal shavings. Unless of course you send out the case to get the bosses cut down. (which can be done, i.e. Don's Dream Machines)

Just thought I'd pass this along since it helps to have an explanation instead of a simple yes or no.

nkh

Newer C-90's had thru bolts instead of studs also.

Nathan: It only requires a bit of clearancing to fit the lifter bodies of a C-90 to the 85 case. Higher lift of the cam and the larger head on the lifter requires it . The C-90 cam is one of the best for performance . It is also steel, not cast. The cam and lifters have to be matched for materials, so you must use different lifters with the steel cam than with the cast cam of the 65- 85. The late model 90 with the through bolts is the better case, as was mentioned.
One interesting thing is that the C-90 will turn the same prop as the 0-200 at a higher rpm. Hmmmmm.
If you want to build the ultimate small Continental for experimental it would be an 0-200 with the C-90 cam, and C85 pistons.
Now you have some serious power. For a small engine, it don't get much better than this. Certified ? No, but it's still a great engine for experimetal.