At the risk of reviving an old thread, the O-320 in my 172 died in the same way: corrosion on the cam lobes. The cam must be removed to repair, which means splitting the case, which is so labor intensive you might as well overhaul the engine. And if you're doing that you might as well replace the engine with an O-360 and enjoy better performance. So that's what I did. The O-360 is very close to the O-320 in size and weight.
The O-320 that failed, I was not the original owner. It had 1250 hours at failure, I bought it with 800 hours. It always had clean UOAs. One cylinder lost compression, and after we pulled that jug we saw the cam. No idea how long it had been in that condition. Could have been like that when I bought the airplane. I flew it every week, but I don't know how long it sat around before I bought it.
This is why airplane engines should be operated on a regular basis. If they sit around, the oil drips down into the pan and exposes internal metal surfaces to corrosion. And aircraft oils aren't overbased with Ca like some automotive oils are, so they are not as effective as neutralizing acids. There is an additive called Camguard that is beneficial, based on independent analysis I've read.
The O-320 that failed, I was not the original owner. It had 1250 hours at failure, I bought it with 800 hours. It always had clean UOAs. One cylinder lost compression, and after we pulled that jug we saw the cam. No idea how long it had been in that condition. Could have been like that when I bought the airplane. I flew it every week, but I don't know how long it sat around before I bought it.
This is why airplane engines should be operated on a regular basis. If they sit around, the oil drips down into the pan and exposes internal metal surfaces to corrosion. And aircraft oils aren't overbased with Ca like some automotive oils are, so they are not as effective as neutralizing acids. There is an additive called Camguard that is beneficial, based on independent analysis I've read.
