cylinder bore finish
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
cylinder bore finish
I wounder how the cylinder bore finish would look like after the rings have seated correct. And if some vertical "scratch" marks in the bore is consider as normal or a sign of that something is wrong.
regards..
regards..
Team Owner
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
were they align honed......or even over-bored? if so, more than by .030"? you may be seeing whats left of the original factory crosshatching. how "vertical" are the vertical marks?
try to get some photos if possible, and other members here can help out.
try to get some photos if possible, and other members here can help out.
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Not over-bored. Just the "normal" honing process that is included when using new pistons and rings.
What I can see now in the bores is crosshatching from what I belive is from the honing process. As well as som vertical "scratch" marks that I belive comes from the piston.
Its moly rings that I use.
i will try to take som pics.
Thanks
What I can see now in the bores is crosshatching from what I belive is from the honing process. As well as som vertical "scratch" marks that I belive comes from the piston.
Its moly rings that I use.
i will try to take som pics.
Thanks
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
The scratches are not deep, I cant feel any resistent when I go over them with my fingers.
Here are som pics.
I dont have any clue on what could have caused those scratches? None synth oil whas used during break-in and the ring gap as well as the piston to wall clerance whas within manufacture spec?
Here are som pics.
I dont have any clue on what could have caused those scratches? None synth oil whas used during break-in and the ring gap as well as the piston to wall clerance whas within manufacture spec?
Le Mans Master
Joined: Oct 2004
Posts: 5,841
Likes: 19
From: CLT, North Carolina
Normal, everything looks fine. I see more smear marks than scratches in your pictures. A honed finish is not perfectly smooth. It consists of a series of peaks and valleys which can be measured by special equipment and graded for smoothness in units of measure called RA. Smears and minor bore scratching happens after a new assembly gets run-in; small fragments of metal are torn by the rings off the peaks left by the honing process and gets caught between the piston and cylinder wall. These small fragments or even the new piston itself will slightly burnish your fresh hone job resulting in the marks you see which are harmless.
Last edited by Greg Gore; Mar 15, 2006 at 04:58 PM.
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Thanks.. 
When I whas out taking the photos I whent over the bores whery careful again.
On no:3 cylinder bore i got a 4mm long vertical cylinder bore "scratch" that I can feel with my fingernail, its not deep, but I can feel it when I move my fingernail horizontal over it.
You can se it on picture 6, if you look close you can se one scratch that is more "clear" then the others, in the middle.
Thanks for the feedback so far
When I whas out taking the photos I whent over the bores whery careful again.
On no:3 cylinder bore i got a 4mm long vertical cylinder bore "scratch" that I can feel with my fingernail, its not deep, but I can feel it when I move my fingernail horizontal over it.
You can se it on picture 6, if you look close you can se one scratch that is more "clear" then the others, in the middle.
Thanks for the feedback so far
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Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by Greg Gore
Normal, everything looks fine. I see more smear marks than scratches in your pictures. A honed finish is not perfectly smooth. It consists of a series of peaks and valleys which can be measured by special equipment and graded for smoothness in units of measure called RA. Smears and minor bore scratching happens after a new assembly gets run-in; small fragments of metal are torn by the rings off the peaks left by the honing process and gets caught between the piston and cylinder wall. These small fragments or even the new piston itself will slightly burnish your fresh hone job resulting in the marks you see which are harmless.
Large Impressive Member
Joined: Jul 2003
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by Pete K
I have seen worse. It is skirt scuffing. Normal
You mentioned running your finger over them, also use your fingernail. I don't think you'll find a problem though, it looks pretty normal.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 14
From: backwoods upstate ny
your engine builder neglected to ''stone'' the ring ends...leaves sharp ''cutting edge'' which ''machines'' vertical grooves as seen here
common error
slight increase in oil consumption will result
carbon build-up indicates enough running time has been experienced to wear off cutting edge of rings--damage is done and won't get any worse
run it
common error
slight increase in oil consumption will result
carbon build-up indicates enough running time has been experienced to wear off cutting edge of rings--damage is done and won't get any worse
run it
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by Corvette Kid NC
You mentioned running your finger over them, also use your fingernail. I don't think you'll find a problem though, it looks pretty normal.But perhaps that just one of the minor bore scratching that happens after a new assembly gets run-in, just as Greg Gore told me
Thanks for the help. And to calm me down
Best Regards
Last edited by devilfish; Mar 15, 2006 at 10:51 PM.
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by redrose
your engine builder neglected to ''stone'' the ring ends...leaves sharp ''cutting edge'' which ''machines'' vertical grooves as seen here
common error
slight increase in oil consumption will result
carbon build-up indicates enough running time has been experienced to wear off cutting edge of rings--damage is done and won't get any worse
run it
common error
slight increase in oil consumption will result
carbon build-up indicates enough running time has been experienced to wear off cutting edge of rings--damage is done and won't get any worse
run it
Dont follow you there.
Thanks
Pro
Joined: Nov 2005
Posts: 658
Likes: 12
From: Clearwater Fl
Originally Posted by devilfish
Can you explain a bit more about "''stone'' the ring ends".
Dont follow you there.
Thanks
Dont follow you there.
Thanks
When ring end gap was set, a shap edge was left on the ring instaed of rounded off ( deburred ).
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 14
From: backwoods upstate ny
if you slide your finger tip across the corner of a new ring at the end gaps you will ''catch'' your finger on the sharp point left from manufacture...this sharp corner should be ''broken'' very slightly with a whetstone to ''dull'' the cutting edge....geometry of expanding circular ring exposes ring end to become a cutting tool - how good it cuts depends on how sharp it is...sort of reverse idea to using a sharp drill bit vs a worn one because in the engine you don't want it to cut in
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by obnoxus
When ring end gap was set, a shap edge was left on the ring instaed of rounded off ( deburred ).
And the other "marks" I see is skirt scuffing, and thats normal, as some already mention?
Last edited by devilfish; Mar 15, 2006 at 11:30 PM.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 14
From: backwoods upstate ny
''skirt scuffing'' is only ''normal'' because so often the work is not done properly that ''junk'' becomes the norm.
after honing, the cross-hatching pattern should be ''plateau'' finished by light pressure with a fine grit to remove the torn and overlapping metal fractures created in the honing procedure...left untouched this material is knocked off by the piston ring and abrades the piston skirt and cylinder wall before eventually working its way out....some ''engine builders'' skip this procedure
after all machine work is completed, the engine block should be thoroughly washed to remove potentially damaging grit...this is a task which requires more time and effort than some care to devote themselves to...grit finds its way into cylinder bores and engine bearings with undesireable effects
after honing, the cross-hatching pattern should be ''plateau'' finished by light pressure with a fine grit to remove the torn and overlapping metal fractures created in the honing procedure...left untouched this material is knocked off by the piston ring and abrades the piston skirt and cylinder wall before eventually working its way out....some ''engine builders'' skip this procedure
after all machine work is completed, the engine block should be thoroughly washed to remove potentially damaging grit...this is a task which requires more time and effort than some care to devote themselves to...grit finds its way into cylinder bores and engine bearings with undesireable effects
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by redrose
''skirt scuffing'' is only ''normal'' because so often the work is not done properly that ''junk'' becomes the norm.
after honing, the cross-hatching pattern should be ''plateau'' finished by light pressure with a fine grit to remove the torn and overlapping metal fractures created in the honing procedure...left untouched this material is knocked off by the piston ring and abrades the piston skirt and cylinder wall before eventually working its way out....some ''engine builders'' skip this procedure
after all machine work is completed, the engine block should be thoroughly washed to remove potentially damaging grit...this is a task which requires more time and effort than some care to devote themselves to...grit finds its way into cylinder bores and engine bearings with undesireable effects
after honing, the cross-hatching pattern should be ''plateau'' finished by light pressure with a fine grit to remove the torn and overlapping metal fractures created in the honing procedure...left untouched this material is knocked off by the piston ring and abrades the piston skirt and cylinder wall before eventually working its way out....some ''engine builders'' skip this procedure
after all machine work is completed, the engine block should be thoroughly washed to remove potentially damaging grit...this is a task which requires more time and effort than some care to devote themselves to...grit finds its way into cylinder bores and engine bearings with undesireable effects
If I remember right, Im pretty sure I saw those kind of marks on my orignial engine, when I tore that engine apart. Does that mean that GM also skip this procedure. Or perhaps that whas the result of another issue, i dunno.
Thanks
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 14
From: backwoods upstate ny
big problem with production blocks occurs at casting corners (gm does a lousy job of ''snagging'' their castings)...typically you can break off tiny bits with your fingertips at many places inside a production block..(deburring the block with a die grinder is standard procedure with good engine builders)..vibration and thermal cycling liberate the ''tiny bits'' to seek mischief.
does gm address the ring ends? ..i don't know...vertical grooves in the cylinder wall that correspond with ring end travel might indicate they didn't
does gm address the ring ends? ..i don't know...vertical grooves in the cylinder wall that correspond with ring end travel might indicate they didn't
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by redrose
big problem with production blocks occurs at casting corners (gm does a lousy job of ''snagging'' their castings)...typically you can break off tiny bits with your fingertips at many places inside a production block..(deburring the block with a die grinder is standard procedure with good engine builders)..vibration and thermal cycling liberate the ''tiny bits'' to seek mischief.
does gm address the ring ends? ..i don't know...vertical grooves in the cylinder wall that correspond with ring end travel might indicate they didn't
does gm address the ring ends? ..i don't know...vertical grooves in the cylinder wall that correspond with ring end travel might indicate they didn't
So to sum this up.
The condition of my engine is not unik and is due to "cutting corners" when it comes to building it?
My engine builder neglected to ''stone'' the ring ends. And that caused the scratches. But as you said, enough running time has been experienced to wear off cutting edge of rings and won't get any worse?
And beacuse of this I might notice a slight increase in oil consumption?
Same goes for the skirt scuffing. Not unik and not "dangerous" but could be avoided if more effort whas used to deburring/cleaning the block?
Any downside of this?
In other words, stop worrie and drive the car
