IO-540 oil darkens earlier after #4 IRAN

lucius

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Had IRAN on #4 due to what looked like an onset of a burned exhaust valve, albeit in hindsight, probably not necessary. After IRAN, and after the initial break-in, and first oil change, I noticed that oil darkens much earlier than before. Oil is Phillips 25W-50. Previously, oil darkened noticeable after 40 hours. Now after 15 hours. Oil consumption, however, has remained unchanged and is about a quart per 10 hours. Engine has 2000 hours since overhaul. At dip stick level, I operate between 8 and 9 quarts.
I have never had fouled plugs at runup. Using Tempest massive. But now got it twice on #4. I lean aggressively during taxi, and operate the engine usually between 70-75% closer to max EGT or 10 degrees LOP. That's the IRAN replaced all rings, I am looking for suggestion what to do next, and possible explanation. What I do understand is that oil darkens quicker upon larger amount of blow-by. Thank you!
 
If it has only been 15 hours on the new cylinder and the oil has darkened, give it some more time, it should get better, if not I think you know the answer.
 
Thank you 1RTK1. What is "giving it more time" going to change? Since the rings are new, I would think there should be less blow by from the get go, no?
 
Thank you 1RTK1. What is "giving it more time" going to change? Since the rings are new, I would think there should be less blow by from the get go, no?

New rings on most internal combustion engines need some time to wear in and mate/seal with their new cylinder finishes.
 
Thank you 1RTK1. What is "giving it more time" going to change? Since the rings are new, I would think there should be less blow by from the get go, no?

The rings should be fairly well seated by now as mentioned, it does take a little time depending on the cylinders (chrome, steal etc.), but you still have the original oil in from the break in process if I understand correctly.
After the first oil change things should straighten out.
 
Thank you! Original break-in oil was changed after 15 hours. The darkening has slowed. Now it took 30 hours (from 15) to reach the same dark color. An improvement, but still not where it was before. Oil consumption is as much as before, which is 1 quart every 10 hours. I am going to see if it further improves, and have oil sample sent for oil analysis.
 
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