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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Tore down the motor to swap heads and cams and when it was going back together I noticed a wear pattern where the pistons and cylinders were scraping directly. I thought the rings would have prevented this contact pattern, so I re-indexed them as everything went back together...but its got me curious.
Anybody seen this type of wear before, is it normal or should it be addressed?
How many miles on that piston? Do both look like that?
It should be addressed. Looks like cylinder/piston fitment is off; cylinder bore not true. Measure cylinder bore in torque plates to verify but it appears boring .010" over and installing new pistons and ring pack is in order.
Both front and rear cylinder & piston looked similar...about 5,500 miles.
Not good; check it out as it will only get worse. Might want to send an oil sample to Blackstone for analysis or catch some oil in a clear container and hold it up to the light to see if you can see any shiny stuff floating in the oil.
That is excessive scoring on the pistons and the bore. It is common to see some marks in a section of the block from the crank rolling over top dead center which will leave marks on the skirt but those pistons rub from top to bottom. Since you can't see the teflon coating on the piston I would say it is due to excessive heat. Pistons will swell in the socket from excessive heat causing them to rub. The excessive heat could be from a bad tune running too lean. I personally would split the cases to make sure the metal filings did not damage anything
Could be from heat but I don't see any evidence of heat on the rings and lands. There is something funny looking at the top ring land that is partially obscured by the ring; not sure what it is though. I don't think there was any coating on the skirt; teflon coating normally covers the full skirt. Definitely something is amiss though. The "knock" points to poor piston to cylinder fitment IMHO.
I thought I was looking at a stock piston which has grey teflon coating on the skirt. Those pistons appear to have additional grooves cut into them. Not something I am using. As for the knock points it is more common when using low silicone or forged pistons. The lower the silicone in a piston the more it will swell with heat 2618 pistons need more piston to wall clearance and will slap on cold starts. Hypereutectic pistons need little space so it is more eco friendly and a quieter piston.
Looks like a break it in like your going to ride affair to me. Piston skirt galling that low miles is usually a sign of heat & high RPMS very early in the engines life.
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Piston/ cylinder scoring
