Can carbon score a cylinder and put fine scratches in bearing? I'm watching a guy rebuild an Alpina B7.
Carbon scoring
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MolaKule
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Carbon can be soft or hard, depending on its phase and composition but yes, hard carbon can definitely scratch metals.
I had a remote-control model airplane engine that had many hours of use on it and had significant amount of carbon built up inside the cylinder on the lip around the cylinder between the highest area the piston went to and the head, and also on the inside of the head. I used some cleaner to break loose the carbon, and some of it managed to badly scratch the cylinder and ruined the compression and destroyed the engine. It went from being a usable engine that was not performing to maximum new like ability, to a piece of junk. So yes, carbon that breaks loose can seriously damage an engine.
Saw it all the time at Acura with carboned up piston rings. Leave it too long and the cylinder liners are toast.
Carbon scoring is a real issue; heavy-duty and large-bore engines often use an "anti-polishing ring" at the top of the bore. It's sized to basically scrape carbon from the top sides of the piston above the top ring as the piston reaches TDC each stroke, so that the carbon which forms does not grow enough to contact the cylinder bore. After the ring wears, usually it can be turned over during an inspection then replaced when worn out.
20.40 mark. He goes through a couple of cylinders and shows the scoring. He's German (Frankfurt) but his english is exceptional.
Thanks. And 22:16 showed the other bank.
Question: When describing the second bank & when tallying the overall damage, he used the word "destroyed" three times. What was the negative result of all that scoring? Unacceptable oil consumption? Or lead the engine to seize up? or....
Question: When describing the second bank & when tallying the overall damage, he used the word "destroyed" three times. What was the negative result of all that scoring? Unacceptable oil consumption? Or lead the engine to seize up? or....
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Ultimately he was concerned that the engine would start burning oil after he'd sorted out everything (ex timing chain service). This is an Aluminum-Silicon block without iron sleeves. The walls are acid-etched to expose the hard silicon which gives the walls a dull color. There are only a couple of shops in Europe which have experience with this type of block and we'll know the results in his next episode.
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