I have a 455 that keeps getting oil in cyl 6 after it runs for about 10 mins. Its a rebuilt bottom end that was sold by kenne bell already assembled when first installed it was good for about 500 miles then started smoking like a train tore it off heads cleaned everything up, resealed intake, changed valve on trans, ran 10 mins and started smoking again, took it apart again pulled piston out and didn't see any issues re clocked all rings and reinstalled and same thing ran good for 10 mins then started smoking and missing pulled plug and it was full of clean oil again pulled the engine and put it in the corner for 2 years, Fast forward to now I have put new Heads on it thinking that was the issue with a valve guide but it still did the same thing so its definitely something in the bottom end for sure just don't know if its a block issue or ring/piston issue but it gets alot of oil in it this time it was on a stand so no trans or anything was hooked up I do have another block I could put the rotating assembly in with new rings and bearings but would rather use the current block I'm pretty mechanically inclined but still pretty green on things like this
I think I see a piece of a broken ring in the landing of the piston? About the same width as the darkening in the bore.
That hole is shot (ring seal wise). You will need to hone and re-ring it. "Clocking rings" is not necessary, rings will rotate in the lands with the engine running, and if your gaps are correct, you will not have any more blow by even if they all line up.
So do you think putting all new rings on and rehoning the cylinder would fix it? Could there be any issue with the block causing oil to get it ( crack that i can't see )? Also all the cylinders have the same wear on top and bottom
A crack large enough to permit that much oil would likely be visible to the eye. You can get UV dye and a UV light, or Magnaflux type penetrant/developer and check for about $50 bucks. Take a look at this thread and you will see a similar issue with the wear pattern you see in your engine. https://v8buick.com/index.php?threads/rebuilt-nailhead-in-my-64-wildcat-video-series.353064/ And make sure you measure all the holes/pistons, ring gaps and be certain nothing is out of round or too large. (since we do not know the history of prior work. Was it a recent KB rebuild?).
Check to make sure the bore size, concentricity, and taper are correct for the piston/ ring package you are using. Then look at the piston ring lands. They should be smooth and flat and deeper than ring depth. They should show signs of ring rotation after use. It might be worth your while to measure the piston skirt very closely to check for correct skirt size and profile. (taper and oval shape). Ring land clearance must be correct for each ring and it must be accuraty for the ring to seal properly. After that, look at the rings. The top two rings are not primarily responsible for oil control. The old timers used to call the top ring the compression ring, the second one the oil scraper and the bottom one the oil control ring. Start with the most likely offender first, the oil control ring. Look for sufficient tension from the expander, sufficient end gap, (.030" to .035" would be fine, .010" would be too tight). make sure the rails aren't twisted or deformed in any way. The scraper ring is tapered on the face if its cast and the sharp corner is meant to be down towards the oil control ring. It is responsible for metering the correct amount of oil for the compression ring to perform correctly. It is not able to perform all of the oil control for a cylinder. Your bore pics show that there is uneven wear, and little or no rotation of the ring set as the engine runs. If is measures correctly (with a torque plate installed) you should be able to hone it and go. One old style trick you can use is to measure and inspect the problem cylinder and its components against another one that is performing properly. If you look closely enough, you will eventually see the difference and then be able to repair the defect with confidence.
I would have to agree with Ziggy, that block needs to be bored I suspect. Maybe try your other block and see if it check out at the machine shop and go from there.
