Piston ring broke, scuffed up cylinder a little
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Mountain Pass
Joined: Apr 2021
Posts: 134
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From: Laredo Texas
Piston ring broke, scuffed up cylinder a little
Chasing a slightly duff idle, we ran compression checks. Cylinder 3 was slightly low, consistently. The truck ran fine but idle was not quite right. Especially with a 4" straight exhaust.
We pulled that head and checked the valves, all look good. We turned over the crank by hand and inspected the bores. There is minor scuffing on the #3 cylinder wall, but hone marks still present at 315k miles there and everywhere else. One #3 ring has an imperfect area which you can see in the pics. This must have caused the wear on the piston, and it must be recent, because engine oil analysis came back fine a year ago. We also found an oil squirter that had some loose. #7
Pics below. We decided to install one new piston & rings, and hone that cylinder out again. I had a spare rebuilt forged-rod block set aside for a major issue, but my cousin wanted to put it in an old Lincoln sedan instead. I still have one forged rod OBS motor on the shelf, and one forged-rod SD motor in a parts truck, but will save those for full rebuilds one day.
In the meantime, I'm just patching up this PM-rod motor with one cylinder. I know the PO and how he maintained it. I don't want to do a full rebuild on a PM motor.
We pulled that head and checked the valves, all look good. We turned over the crank by hand and inspected the bores. There is minor scuffing on the #3 cylinder wall, but hone marks still present at 315k miles there and everywhere else. One #3 ring has an imperfect area which you can see in the pics. This must have caused the wear on the piston, and it must be recent, because engine oil analysis came back fine a year ago. We also found an oil squirter that had some loose. #7
Pics below. We decided to install one new piston & rings, and hone that cylinder out again. I had a spare rebuilt forged-rod block set aside for a major issue, but my cousin wanted to put it in an old Lincoln sedan instead. I still have one forged rod OBS motor on the shelf, and one forged-rod SD motor in a parts truck, but will save those for full rebuilds one day.
In the meantime, I'm just patching up this PM-rod motor with one cylinder. I know the PO and how he maintained it. I don't want to do a full rebuild on a PM motor.
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