The Cessna 120-140 Association Forum

My C85 engine broke a valve and kept running for about 4 minutes then quit on final approach (Sept 2nd). The piston cracked but all the resulting rubble never got past the broken piston. The crankcase oil was full before and after the flight. The connecting rod was twisted, and the piston face was badly pock-marked, not to mention the “reshaped” broken valve, and battered plugs. The vibration was AWEFULL, but the C85 did get me home, though not to the ground.
My engine is fixed with a new Millinimum cylinder and all the guts (connecting rod and up). It was #2 cylinder (back left). I have 5 hours on the new hardware. I trust the situation, but my wife, and steady travel partner, does not.
The engine is about 1400 hours SMOH. My mechanics says the engine should be good for another 400 hours, most likely. My A&P/IA is highly respected and trusted in this area, by me and everyone I know. This engine passed “The Annual” compression check just fine, but clearly the valve did not reveal itself. So I wonder “are all the other valves ok?”. How do you know when it is time for major overhaul?
Bill Suter

Bill wrote: "So I wonder 'are all the other valves ok?'. How do you know when it is time for major overhaul?"

A lot (most?) of us prob go for the major when oil leaks get to a point of being unacceptable. Mine was 2700 SMOH...with a lot of leaks. When we disassembled, the appearance of "innards" & some quick measurements of crank and camshaft led my IA to say "Mac, we've torn down a perfectly good engine". Of course, there's definitely need at some point to have every part inspected, "renewed" or overhauled or replaced + case & acc'y case "overhauled". ...ideally, of course, before a failure of any kind "happens" .

Just curious, Bill -- how old are your (other 3 cylinders)? Are they Millenniums (or other brand)? ...been overhauled? I recall early on having one of my original Continental cylinders with a leaking/burned exhaust valve overhauled. The shop installed newer valves in that one and admonished me to pull the other three for valve "upgrades".

BTW, good job of flying the airplane & good for that little Continental to keep puffing 'til you had a runway! This sort of thing can certainly shake our own confidence just a bit and, understandably, that of our traveling partners. As Victor mentioned in the related thread, these little engines are incredibly dependable and just very seldom fail. We all know that we almost always get advance "warning" -- via oil analysis trends, metal evident, borescope "alert", excessive oil use, poor compression, rough running, etc. and etc.. "Odds" are truly with us. And, if "it" does happen, some time behind a now well running (again) engine will hopefully re-breed confidence, for us and for our right seat partners.
Mac

Good to hear of the good outcome.

What was the state of the cylinders when the engine was overhauled last - new or overhauled? I have a prejudice towards new Millenniums only.

Thanks for the replies. I am going to dig as much info from my logs as I can and reply again. They are locked at the airport at this moment.
Here is what I do know:

All 4 cylinders indicated “Continental” on the valve covers. Now the #2 cylinder is a Millennium.

I am glad to hear that Millennium has a good reputation.

I have always been curious about the details of the major overhaul. I must look again, because I looked 10 years ago and did not see those details. I would like to know. My plane came from Pescott, AZ with 300hrs SMOH.

In the hangar, it seems to not drip oil at all, like it did before the valve broke.

I have 5.6 hours on the new hardware and have added one quart. The 5.6 hours includes the first 15 minutes at 900 rpm and 4 minutes at 500 rpm on the ground.

It now runs like it did before. I trust it, and my wife says she will be OK with the engine if she can talk to my A&P/IA. That is progress, and I think she will be fine after some air-time over the flatlands of NW Ohio.
Bill Suter (N1916V) Bluffton, OH (5G7)

If it has good oil pressure and gets it pretty quickly after starting and has no major leaks, I’d be tempted to remove the other three cylinders and either have them overhauled with new guides and exhaust valves or replaced with Millenniums.
If it barely holds 30 PSI in cruise and doesn’t get oil pressure for quite awhile after starting, and or leaks like a sieve then it’s likely time to overhaul.

I don’t put much faith in oil samples myself, after managing fleets of military aircraft for 15 years that were regularly sampled.

Geeze Bill, I'm glad everything turned out ok on this one. We missed you down in Atlanta!

To all interested parties. Here is the "post script" to the engine failure.

My C85 was majored in 1997 (24 iyears ago). The only thing I see in the docs is that they used one new bearing set (of 8) and 4 "cylinder kits". They also reground the lifter body, camshaft, replaced bushings on a connecting rod and dis some case repair. I can not see anything specific about the valves.

I have decided to fly my plane "as is", mostly alone, at this time because I trust it. To reassure future passengers, especially my wife, I am looking to do a major overhaul, even though the engine is at about 1,400 - 1,500 hours. My A&P & I/A recommends Klein Aviation in Michigan, but it sounds like I must wait until April and still hope I get to the top of "the list". I am northwest Ohio. Does anyone have a recommendation for C85 overhauls in this neck of the country?

Victor, I was very frustrated to have missed the convention this year, but I am looking forward to seeing everyone again next year. In retrospect, it is lucky I was not over the Smokiy Mountians when the valve broke, but I will be back.

Thanks everyone for your kind words and advice. Bill Suter Bluffton, OH (5G7)

I am using G&N in Griffith IN.
They are doing a C-85 stroker upgrade for me but seem to be having problems getting new cylinders.

The FBO I worked at many years ago used them and had good luck with them.

Rick