Glazed Cylinder

[jimboe]

I just did the annual on my Champ last Wed and found the bottom #3 spark plug soaked in oil. I had noticed some slight plug fouling during run-ups in the past 20 hours and this looks like the source.

I have a C-85-12 with 0200 crank set-up and did a complete overhaul about 100 hours ago, including new Millenium cylinders. I used straight Aeroshell mineral oil for the 1st 50 hours and switched to the ashless dispersant multi-viscosity "Plus" after that.

The new engine tended to run hot in the summer with oil temps up to 220-degrees so I installed a Steve's Aircraft oil cooler which keeps the temp below 200, but in the winter I have to block the airflow to it to get up to 160-170 oil temp.

My mechanic pulled the #3 cylinder and there was about a spoonful of oil sitting in the combution chamber. He said the cylinder wall was glazed and the rings had not completely seated, except the top ring which provided for a good compression check. He ordered a new set of rings and will re-hone the cylinder.

My engine has run flawlessly since the rebuild and burns 4.7 gal/hr. I'm trying to understand why there is oil getting into that combustion chamber NOW. I also wonder about the condition of the other cylinders and if they are likely to have the same problem so long after the rebuild. Any suggestions for strategies after we put it back together with the new rings?

One other thing that may or may not be a factor is all the spark plugs indicate the carburation is a little rich - dry, dark deposits, yet the engine runs and starts easily except when it's really cold outside. I've never had to clean a plug except during annual. My base airport is at 2,000 feet. I have the Stromberg carb with the steel needle seat that spews fuel everywhere. There is some black soot on the tips of my exhaust outlets, but I have not noticed any blue oil smoke. The engine will backfire if I pull the power off all the way to glide and I will be replacing the exhaust gaskets and checking for other leaks.

Sorry if I gave too much info. I've lost a little faith in my engine and would like to regain the confidence in it.

Thanks for your advice,
Jim

[Paul Agaliotis]

Jim,
Put it back on mineral oil for a while. I look for a decrease in oil temp to show the engine broke-in. I like to use Aeroshell W80 for lubrication. Used it for many years with no problem, changed at each 50hrs or Annual. Stay away from car gas and lean it down a bit.
Paul

[Sgt. NCSHP]

When I bought my 7DC it had 62 SMOH on a C-85 with 0200 crank. Oil consumption was a quart every 4 hours on so I took Paul's advice and switched back to mineral oil for another 50 hours and ran it about 75 rpm below redline the entire 50hrs . Oil consumption went to a quart every 7 hrs and oil temps went down . Remember in the old days these things ran strictly on mineral oil so it aint gonna hurt it. IMHO

[jimboe]

I appreciate the advice, guys. I'll pick up some Aeroshell 80 straight mineral oil tomorrow. We'll hone the cylinder and put it back together with fresh rings, then no more putting around at 2,200 rpm for a while.

I'll ask Steve about leaning the carb - I imagine there is an air or fuel mixture screw. Which direction to lean?

Thanks,
Jim