GRUMPYVETTE?
What causes a scratch, or gouge like this?
This engine has about 90 minutes of run time on it, it was professionally rebuilt by a reputable shop.
Heads were removed, due to rocker/valve stem damage, and this is what I see inside. (valve problems were on #2 and 4, so this is not related to that)
This is the #3 cylinder, #1 also has a scratch, but #3 is the worst.
When I was running it in the driveway to break-in the cam, I noticed that there was alot of oil collecting where the exhaust was blowing down onto the concrete. The drivers side bank was twice as much as the passenger's, and this is the side where the scratches are. I thought it was interesting, and I had never thought about it, but I just figured that an engine must blow a lot of oil, until the rings seat.
Anyway, what do you think? is this an old scratch that was not bored out, or is this new damage that I did to myself? And, from what?
Id need a much clearer picture and a magnifying glass OR ,Using good light and a jeweler's loupe, but the scratches appear to be ring the result of the ring ends not being properly stoned or deburred,(ring ends not deburred) or the engine might have just had loose casting debris, or chips from cylinder head machine work in the cylinder heads that broke loose, but I strongly suspect its ring ends not being deburred because if you look closely the scratches seem to have a lighter & shallower scratch parallel in both cases thats about .020 away from the deeper scratch
a good magnifying glass OR ,Using good light and a jeweler's loupe,will easily provide the answer here,as to if the scratch was there when the rings were installed or was created during the engine break-in.. look very closely at the scratch edge burrs
you'll see which was made last over the old hone marks or new hone marks over the old scratch, and chances are EXCELLENT that its a new scratch over old hone marks for two reasons
notice the scratch ends exactly where the top ring wear on the bore wall ends on the pistons upstroke
(1) if the scratch was there when they honed the bore they would have honed it longer
(2) if the hone was done over the scratch the edge of the scratch would be much more rounded and less distinct
now some one might ask if the scratches are about .927" apart indicating a loose piston pin contacting the bore. but while at first glance a loose piston pin MIGHT be to blame , but I doubt it looking at the pictures, because theres really 4 parallel scratches and the piston pin height never gets that high in the bore on most pistons
related info
viewtopic.php?f=53&t=247
viewtopic.php?f=53&t=3897
viewtopic.php?f=53&t=2837&p=7989&hilit=bore+distortion+hone#p7989
viewtopic.php?f=53&t=509
viewtopic.php?f=51&t=125&p=12993&hilit=hone#p12993
viewtopic.php?f=53&t=4602
What causes a scratch, or gouge like this?
This engine has about 90 minutes of run time on it, it was professionally rebuilt by a reputable shop.
Heads were removed, due to rocker/valve stem damage, and this is what I see inside. (valve problems were on #2 and 4, so this is not related to that)
This is the #3 cylinder, #1 also has a scratch, but #3 is the worst.
When I was running it in the driveway to break-in the cam, I noticed that there was alot of oil collecting where the exhaust was blowing down onto the concrete. The drivers side bank was twice as much as the passenger's, and this is the side where the scratches are. I thought it was interesting, and I had never thought about it, but I just figured that an engine must blow a lot of oil, until the rings seat.
Anyway, what do you think? is this an old scratch that was not bored out, or is this new damage that I did to myself? And, from what?
Id need a much clearer picture and a magnifying glass OR ,Using good light and a jeweler's loupe, but the scratches appear to be ring the result of the ring ends not being properly stoned or deburred,(ring ends not deburred) or the engine might have just had loose casting debris, or chips from cylinder head machine work in the cylinder heads that broke loose, but I strongly suspect its ring ends not being deburred because if you look closely the scratches seem to have a lighter & shallower scratch parallel in both cases thats about .020 away from the deeper scratch
a good magnifying glass OR ,Using good light and a jeweler's loupe,will easily provide the answer here,as to if the scratch was there when the rings were installed or was created during the engine break-in.. look very closely at the scratch edge burrs
you'll see which was made last over the old hone marks or new hone marks over the old scratch, and chances are EXCELLENT that its a new scratch over old hone marks for two reasons
notice the scratch ends exactly where the top ring wear on the bore wall ends on the pistons upstroke
(1) if the scratch was there when they honed the bore they would have honed it longer
(2) if the hone was done over the scratch the edge of the scratch would be much more rounded and less distinct
now some one might ask if the scratches are about .927" apart indicating a loose piston pin contacting the bore. but while at first glance a loose piston pin MIGHT be to blame , but I doubt it looking at the pictures, because theres really 4 parallel scratches and the piston pin height never gets that high in the bore on most pistons
related info
viewtopic.php?f=53&t=247
viewtopic.php?f=53&t=3897
viewtopic.php?f=53&t=2837&p=7989&hilit=bore+distortion+hone#p7989
viewtopic.php?f=53&t=509
viewtopic.php?f=51&t=125&p=12993&hilit=hone#p12993
viewtopic.php?f=53&t=4602