Hello,
Following a VNIP I finished 25 hours running-in period of my O-360-A1A (with mineral oil 80), and since I put usual oil spark plugs bottom do not work (200 RPM drop on "L" selection), they are fouled with oil.
We opened the intake pipes and we found oil in it (from where does it come ?).
Does it say that the running-in was not well done? During the lapping with mineral oil I flew 20 Hg MP and 2300 RPM instead of 75-80 % of the power. I didn't know running-in must be done at higher power.
Mechanic advise to resume a new running-in period at 75-80 % of power.

Thanks for your knowledge.

Michel
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The re-run, as with any break-in should be done with 75% as a minimum power setting. The limit on power setting is CHT. Be prepared for the cylinders to come off to be honed and new rings on the pistons.

The attached ECI document is an excellent discussion on break-in procedures:

BreakInInstructions.pdf

(448.84 KiB) Downloaded 34 times

Paul, As JIm has mentioned, unfortuneately you might have coked or baked the oil into the honed ridges in your cylinder walls and
you probably have to re hone them. As far as oil in the intakes, that doesn't sound right even if you have oil seeping past the rings.
How much oil was in there?
Good luck with the breakin retry. Hope it works, real pain to have to rehone them.

Gary

+1 on the other comments. Next breakin leave the throttle open and reduce rpm to 2500 to climb. This keeps the bmep higher and helps seat the rings. Cruise at 75% with a square power setting. A long time ago in the days of chrome cylinders I noticed that engines with fixed pitch props always broke in much quicker than the same engine in with a constant speed. This is because we all used to pull the throttle back to 25" where on the FP ones the throttle stayed open. Higher MP yields higher bmep. Charlie Melot Zephyr Engines

When I broke in my O/H'd engines by Zephyr, I used Charlie's method and they broke in in less than 10 hours. I had to work hard to get 75% because it is so darn hot in Texas in July, the density altitudes are high. I saw a lot of sunrises.

so when looking for 75%, be sure to consider density alt.

Merci beaucoup !
Thanks a lot to all: Jim, Gary, Patricia, Charlie
I carefully debrief in detail all your advices before starting this second break in
12 liters of Mineral Oil 80 should arrive today in Abidjan.

Thanks again

Michel

Dear Comanche Flyers,
The story ends well and I think it is worth to inform you:
It seems second break-in succeeds.
After this second breaking (25 hours again at 75-80 %), I flown 10 hours with D100 oil. Spark plugs stay dry and clean; no oil fouling and no abnormal drop during magnetos selection. I use to taxi with a little of mixture, the same in cruise flight.
Living in Africa, I am happy not to have to send my cylinders abroad.

Michel
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