One area often over looked after an
engine has been bored and honed is the bottom of' the cylinder.
If this burr is not removed it can cause piston scuffing.
The sketch below depicts a piston at the bottom of the stroke.
In newer engines much of the piston
skirt protrudes from the bore at the bottom of its travel
and when it begins its upward travel it cocks or cants in
the cylinder. If there is a burr at the bottom of the cylinder,
aluminum will be spalled or rubbed off and cast iron transferred
to the aluminum. These particles can break through the oil
film and scuffing is started. In some cases it may get progressively
worse until the engine fails.
Crocus cloth, Scotch Brite®, or some
similar material can be used to remove the burr.
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