Excessive oil on plugs. What to do?

[Steve Barnes]

I just completed a complete engine overhaul. I sent the cylinders out to a large well known cylinder rebuilder. I now have 32 hours since overhaul and all the bottom plugs have excessive oil on them. Some more than others.

This is the fourth engine engine that I have broke in. The first 3 ended up as they should. I used the recommended breakin procedure. The CHT's came down as they should after a few hours but was having fouled spark plugs and hard hot starts. As soon as I added full power on take off the plugs would clear up. First oil change is when I first found oily plugs. Cleaned the plugs changed oil again with the recommended mineral oil. I ran the engine hard for another 22 hours. The plugs weren't fouling as bad as before but was still having difficult hot starts. Drained oil and checked the plugs and all the bottom plugs were oily.

Should I continue to run hard with mineral oil?
Pull the cylinders off and send back to the cylinder rebuilder?
The cylinders are the original steel barrels as purchased from Lycoming 1200 hours ago.
The only thing I could think of is the rebuilder installed the wrong rings in the cylinders.

Any advice from you Lycoming experts would be much appreciated. Steve

[rocketbob]

Tell us what you did for break-in. Sounds like you glazed the cylinders. Short runs, keeping under 300 CHT works best.

Running hard during break-in will glaze the cylinders.

If they're glazed, pull the cylinders, re-hone, and start over.

[N941WR]

Originally Posted by rocketbob

Tell us what you did for break-in. Sounds like you glazed the cylinders. Short runs, keeping under 300 CHT works best.

Running hard during break-in will glaze the cylinders.

If they're glazed, pull the cylinders, re-hone, and start over.

That is the exact opposite of what Mahlon recommended.

He recommended full power, full rich, below 3000', which is what I did on both my engines.

[jrs14855]

Mahlon's method is the gold standard. The rings are likely to never seat at low power settings. 400 momentary CHT on initial break in will not cause any problems. Higher CHT's after break in will not cause damage. Apples to Oranges but in the desert SZ the big Continentals run red line CHT and Oil from taxi to top of climb. They still usually go to TBO.

[rocketbob]

This is what I do and have a bunch of engines that don't use oil.

[rocketbob]

Originally Posted by jrs14855

The rings are likely to never seat at low power settings.

Several ground runs staying below 300 CHT will seat the rings. This is per the ECI breakin instructions.

[Bavafa]

Originally Posted by N941WR

That is the exact opposite of what Mahlon recommended.

He recommended full power, full rich, below 3000', which is what I did on both my engines.

Lycoming also recommends limiting the ground run up and high power run, I did a 30 minute run at high power first to check there is no leak or issues and then a two hour run at full power but keeping the CHT below 400. The last 15 minutes of the two hour run, I changed power setting to different ranges.
This has been their recommendation on both of my engines.

[lr172]

Originally Posted by rocketbob

Several ground runs staying below 300 CHT will seat the rings. This is per the ECI breakin instructions.

+1

The real risk of glazing is in the first 15-30. Minutes, as the initial ring break in creates a LOT of heat. Best to not push too hard here. After the first cht drops then push it harder for balance of break in. This is why mahlons approach works. The initial ring seating is in controlled conditions. Rings will seat fine if secondphase of seating gets 75% power

[RV6_flyer]

Here is what Lycoming recommends be done for break-in.

Here is the ECI break-in instructions.

Sounds like you need to pull the cylinders, hone, and start over.