The Cessna 120-140 Association Forum

As mentioned in another post of mine, I'm trying to muster the money (and the courage) to overhaul my engine. I have a 1946 C140 with a C85 with straight exhaust pipes. I have several questions about the whole endeavor...

1) What are some trusted engine shops that people would recommend?
2) What have people paid recently? I've been bracing myself for a $15K bill. Is that reasonable? This is for the engine only. My accessories are in good shape, so I plan to re-install them. And I'm not counting the removal and re-installation of the engine on the airframe in that price, either.
3) If my crankshaft checks good, is it worth it to re-use it? Or is the O-200 crankshaft STC "cheap" enough that it is the better way to go?
4) Should I consider converting to an O-200? I've ruled this out as an option because I assume I would a) have to get a new engine mount, b) not be able to use straight exhaust pipes, and thus c) have to get a C150 exhaust and d) modify my cowling, thus driving up the overall cost of this project. Is all of that true? (Just want to verify that I understand what all is involved in converting to an O-200.)
5) Any thoughts on trying to get a C90? Can you convert a C85 to a C90? Would it be worth the effort?

Any thoughts would be appreciated. Thanks.

Im still in early stages of learning this stuff, so verify anything I say.

Mine has the O-200 goodies on the c85. I have been told most dyno out around 97hp, so darned aweful close to an 0-200, but paperwork will still say 85hp... with not having to change a bunch of other stuff seems like it may be a good route to go... if you operate cold weather consider the 150 exhaust with the larger skat tube, as mine will cook you out while I hear many say they can bearly take the chill off in their 140...

Good luck, keep us posted

Ray

central cylinder in Omaha, 2015, mine came to 16,000$, new cylinders, new rebuilt bendix mags

Hi Chris,

I did my C85 8 years ago at Poplar Grove Airmotive in Poplar Grove Illinois. I was happy with the work...maybe not jumping up and down happy, but they did a good job and I’m at 850 hours since and still running very strong. Compressions near 80/80 and 22 hrs per quart oil burn.

I too opted for the O-200 STC. I also had four new ECI cylinders put on as well as a new cam and the crank for the STC. Cost me $19,500 (ugh). The O-200 STC will make a C-85 perform very similar to a C-90. You won’t get any faster cruise performance as the RPM limitations do not change, but you will definitely see a substantial boost in climb performance. You cannot upgrade a C-85 to a C-90 (I think because of the cam) but the STC gets you very close.

I think, at the time, the O-200 crank STC cost around $2,500. ECI nickel carbide cylinders were $1,100 each. It is my understanding that the cylinders (now through Continental?) and the STC all cost considerably more than I paid.

Cost aside, I was very happy with how this all turned out. Actually, if you consider that fuel and oil cost about $23 an hour and the O/H amortized out so far at $24 per hour, I’m still way ahead of the game and flew the last 8 years with a great engine (and probably 10 more to come).

That’s my story. Good luck!

Mike

Our own Randy Thompson does overhauls. I'd contact him to see what he has to offer.

you're going to need a different propeller.

8154 wrote: ↑Mon Jan 28, 2019 7:09 pm you're going to need a different propeller.

??
The engine with the 0-200 STC is technically still a C-85 by the engine manufacturer's type certificate for that model I believe. Seems like my fellow moderator John Cooper mentioned this several years ago on a similar post if memory serves me correct. I'm sure he will chime in on this subject.

The prop requirements for a C85 with the O200 crankshaft mod are the same as a straight C85. The only change you might need or want is a change of pitch. If you're near the upper static limit before the mod you may exceed it after, and so you'll need to increase the pitch to get it back under the limit. You may also want to pitch up to pick up a little more cruise speed with the modified engine. If you (can) leave it as is, the improved performance will manifest itself as better takeoff and climb performance.