Dennis, Continental M47-16 conversion from C75-12 to C85-12 basically called for changing the Stromberg NA-S3A1 and a new prop. The C75 carb had a 1 5/16 venturi and the C85 used a 1-3/8 venturi. The PN for the larger carb was 380172. All in all, the C85 could rev a little higher and thus developed more HP at full throttle.
Wade Halsey Chillicothe,Ohio > >Here's one for you. I have (supposedly) a C75-12. The prop on it, > >according to the tag from the prop shop that was in the paperworks says > >that the prop is a 1C90-LM7252. What engine is this prop supposed to be > >on and what engine do I have? I say this becaused I cann't find > >anything to indicate that my C75 was converted to a C85, but the dip > >stick has been remarked to indicate 4.5 quarts and the plane has a tach > >in it with markings for the 85 horse engine. Makes me wonder. > >Dennis Schmaltz > >Mission, SD > >94715 > > Hi Dennis. I'm looking at the type certificate data...I don't see > a "1C90-LMXXXX" prop at all. All I see that are anything close are > 1A90CF or 1B90CM for the 415D with a 75. Is that what you have? > > If it's not in the engine logs and the data plate, I can't believe > it's been converted. > > Later you said: > >Jim, I checked it earlier and it was still the C75 nameplate, but the > >engine runs like a scawled banshee. In cruise flight, I can easily run > > out to 2550rpm at 5000 ft. msl. I keep it within the redline for a > > 75 though. It will pull 2150rpm on the ground for a full power runup. > >I believe the book says (I'm working from memory here) that the 75hp > >should runup at 2100rpm. Anyway, it sure is a strong running little > >engine. > > The prop may have been repitched to let the engine run faster. > > The TC data I have doesn't mention the correct pitch, only the > min and max static rpm. > > Here's something that might help. Maybe you've seen this already, > but it says "Conversion of the C75 engine to the C85 must be accomplished > per Continental Service Bulletin M47-16 dated June 7, 1948 and the oil > stick recalibrated..." and so on. Maybe there's a way to search the > net and/or call Continental to see what the heck the service bulletin > requires. Then maybe you could tell what you have. > > Let me know if you want me to fax you any of this. I got it off > the net here somewhere, but I'll be darned if I can remember where > it came from. I bet someone else here knows where it is. > Steve Dold ([EMAIL PROTECTED]) http://home.pacbell.net/sdold/
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