02GF74
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 posted on 22/5/08 at 10:08 AM |
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cylinder bore glazing?
1. how can you tell if the cylinder bore is glazed?
2. what is difference between a polished bore and a glazed one?
3. will the honing marks will still be visible for a glazed bore?
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r1_pete
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| posted on 22/5/08 at 10:54 AM |
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A glazed bore is a combination of wear and the 'varnish' like residue from the oil.
As I understand it a polished bore is the result of oil breakdown and is often accompanied by score marks.
It is possible honing marks can be seen in a glazed bore, light re-honing will remove the glazing ready for the new rings to bed into.
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Mr Whippy
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| posted on 22/5/08 at 12:05 PM |
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quote:
Originally posted by 02GF74
1. how can you tell if the cylinder bore is glazed?
2. what is difference between a polished bore and a glazed one?
3. will the honing marks will still be visible for a glazed bore?
1. You can see the brown tint of the glaze
2. A glazed boar will have lots of small vertical scratches in it as it chips off and is dragged up and down with the piston rings, obviously not
ideal. It is unusual for the actual bore metal to be damaged like that unless dirt has got in. Glaze is not a substitute for a polished bore.
3. You may still see the honing lines through the glaze but if you look at the refection in the surface then all you will see is the scratches. Glaze
or carbon will also build up round the piston rings locking them in place so they can no longer seal the bore. I’ve fixed smokey engines simply by
cleaning the rings and ring groves without doing ang further work.
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britishtrident
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| posted on 22/5/08 at 12:07 PM |
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you really need to examine the rings rather than the bores, if the rings aren't making full contact round the whole of thier circumference it
shows up as polish marks on the contact surface of the ring.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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02GF74
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| posted on 22/5/08 at 12:43 PM |
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quote:
Originally posted by Mr Whippy
2. A glazed boar will have lots of small ......
some useful into
CYLINDER CROSSHATCH
Most OEMs and ring manufacturers say the angle of the scratches in the crosshatch pattern should be about 45 degrees to each other, or about 22 to 32
degrees to the horizontal deck surface. The crosshatch angle should be the same throughout the length of the cylinder and not flatten out at either
end.
If the crosshatch angle is too steep, the rings can pump oil or experience excessive rotation which will accelerate wear in the rings and piston
lands. If the crosshatch angle is too shallow, it can have a ratcheting effect as the rings pass over the valleys, preventing the rings from receiving
proper lubrication.
A proper crosshatch will also have enough valleys to retain oil, but not too much oil. The secret here is getting the right amount of retained oil
volume (Vo). If the crosshatch scratches are too deep or there are too many valleys (not enough peaks and bearing area), the engine will use excessive
oil.
The greater the retained oil volume, the higher the oil consumption. This can be caused by finish honing with stones that are too coarse (#150 or
less). On the other hand, if the crosshatch scratches are too shallow or there is too much plateau on the bore surface, the volume of retained oil may
not be enough to keep the rings lubricated; this will cause accelerated ring and cylinder wear. This can be caused by finish honing with stones that
are too fine (#400 or greater).
[Edited on 22/5/08 by 02GF74]
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Mr Whippy
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| posted on 22/5/08 at 12:55 PM |
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can't see you missing that in your engine 
rush typing....
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