camshaft replacement on IO-235

[getonit]

Several months ago I had an exhaust valve break on my C-152. Had it repaired, etc. While the cylinder was off the mechanic took a look inside and told me the camshaft was starting to show signs of spalling. I asked him if it was dangerous or going to ruin anything and he said no, and nothing needed to be done until the engine was not making proper RPM's. Opinions needed on that statement.

2nd question is... What is the best/most economical way to get it repaired? The engine has approx 1200 hours TT and all of the cylinder compressions are good. My knowledge of this is that the case has to be split and everything taken apart. Someone mentioned a field repair or would I be better taking it to an engine shop? I don't want to pay for an overhaul at guessing 10K versus 3k for the other work.

Thanks,
Mark

 

[charlesmelot]

Taking a 1200 hour engine apart can turn into a can of worms. There are often a lot of other things that, while not currently causing any problem, must be addressed. In addition there is some likelyhood that metal from the spalling cam has impregnated the piston skirts. New pistons require new rings, new rings necessitate honing the barrel. Honing the barrel makes it necessary to remove the valves often leading to their replacement. The oil pump and crankshaft may be scored and require repair. You'd be lucky if the parts alone don't cost more than the $3,000 you mention. Charlie Melot Zephyr Aircraft Engines

 

[RafaelThielmann]

Since i've never seen this engine, I suppose it is a boxer-setting engine block, so if it's just a little like the VW-bettle powerplant, it is possible to replace the camshaft without removing the pistons from the cylinders.
But seems like "charlesmelot" knows what he's talking about, so I'm probably wrong.
But there's no harm on asking around about changing it without removing pistons from cylinders....

 

[GravityHater]

But there's no harm on asking around about changing it without removing pistons from cylinders....

Yes, Charles Melot really knows what he is talking about and you cannot do a fast fix of removing the camshaft without dismantling the engine including cylinders - some of the throughbolts hold the cylinders on, anyway its just not possible.

Here is Charlie's website, a top-notch organization:
http://zephyrengines.com/

 

[RafaelThielmann]

Gee Getonit, looks like you are stuck between a rock and a hard place... Or you keep on flying it looking for any problems on the indicators (mixture, torque, oil temp and EGT) or you assume that you'll spend a lot of money by taking out everything and overhauling the engine before the programmed time...
My advice? Since I'm not the guy who likes to take chances on aircraft maintenance I wouldn't fly it knowing that the engine got some issues... specialy if it is a SINGLE-engined aircraft....
Hope you find some good answers to your problems....

 

[Fit59]

I've recently run into the same situation with an O-235 on my Grumman. Fortunately one of my good friends works at an overhaul shop and has offered his assistance. The wearing of the camshaft on the O-235 is a pretty common occurrence. In my case, as was previously mentioned by one of the A&P's on this forum, it has caused more damage to my engine. We have decided to break the engine down and do an overhaul. I was losing plenty of RPM; static was down to 2100, where minimum was supposed to be 2150. This all led to a pretty poor performing aircraft. By the way, my engine was a factory remanufactured engine with only 1250 hours on it. One of the other problems was that the airplane sat for about 6 years... Compression on one of the cylinders was pretty low, 60ish. It will be nice once the engine gets repaired and hung back on the airplane. I'll keep you updated on the cost of my repair, but we are estimating by doing most of the work ourselves and sending out the major components a cost of around 5-6K.

Best of luck!

FIT59