Jim F

Don't forget that the cylinder rocker boss needs to be flat too. Use a small flat file (brake off a 2inch section) so you can get it in the nooks. Use your finger to push the file around the cover mating surface. A high spot will show and needs to be worked until flat. For the stamped steel covers use a small hammer to get the area around the screw hole flat and then find a surface plate, sheet of glass, something flat and set a sheet of sandpaper and lightly move in a figure 8. This will show highs and lows and work so they are consistent. Jim

All the time is good. Look at the intake tubes and touch them. Most of the time a leaking intake pipe will show blue stains around it even if injected. Pay attention to the metal tube that are swaged into the oil sump, look for stains or run and spray WD40 where the tube goes into the oil sump, at idle the rpm will increase. caution (moving prop) Look at all exhaust studs. Pressurize the intake and exhaust with the pressure side of a clean shop vac spray soapy water. Move from easy to hard

you say after a flight and after fueling. Does that mean you hear it after landing and before fueling and after fueling? Kind of hard to hear or maybe it's my ears. Un-cowl and try to get it to repeat. You can close in on where a noise is coming from by using a stethoscope or long screw drive with the handle pressed on your ear. You're working around a moving propeller so be careful and you need someone on the breaks. Place the blade on a what you think is making the noise. The most common noise after starting is usually a hung Bendix drive on the starter. You can start the engine and if you hear the noise shut it down. Look at the Bendix if it's still out (Fwd) its sticking. Clean with contact cleaner and load is up with silicone spary (zero hydrocarbons - oils), this might take multiple application

Hi Paul, I agree that too tight of end gap is most likely the cause, but I would think this would happen in the first 10 hours or so. Not sure i saw the time on this cylinder, but that piston looked like it had more the 300hr on it.

Is there a flight that you remember the oil consumption significantly increase? If so, download the flights just before and send to Savvy and maybe post here. You dont see a lot of broken rings.

Then you were making close to rate power. So i would concur with KSMooniac and ErikJ you would not see a difference in EGT or CHT. The oil went into the combustion chamber and was burnt during the power cycle. Any idea what caused the rings to break?

Well that's interesting, Were you able to make static RPM (~2650rpm) on the runway before take off (before you start rolling)? I would think the EGT and CHT would be low and static RPM would be ~100rpm low

There is one more option to get more clearance, but it has some pit falls. You can release the push rod cover spring clip and push the push rod forward until it hits the push rod. This can give you +.100 additional clearance. make sure you pull the case and cylinder push rod cover seals out of there recesses and spray with pure silicone spray and reseat the push rod cover and reset the spring (both clips)

Offset box end wrench. Some grinding might be necessary. Yes, on fire sleeve. As Skip said, flammable =fire sleeve

What was the unmetered fuel pressure and EGT at 2700, & 34"MAP. The fuel metering unit (throttle body), flow divider, and nozzles are all that's left. When your mechanic increased the unmetered fuel pressure did you see any increase in fuel flow?

I have lots of borescope experience. I don't see the valve seat transition, that tells me that there are deposits built up. It's a little bit of an odd place for a crack, but don't put too much in that statement. I would fly your AC at a high-power setting and take another look. Also, before i would pull the jug I would drop the exhaust and look at the port position side of the potential crack position. Jim

You can use a J-hook pic or a small diameter door hook

I think the 231 and Encore are the same part. Here is a pic, its aluminum and should be painted

YES, Air racing Formula 1 requires a cable between the cylinders bases to the engine mount. Back in the 80s a blade failed, and the engine tore loos from the mounts. The engine was hanging from the hoses. Without the weight of the engine, you are no longer controllable. Jim