Re: Hone Marks was RE: 4-cylinder engine

[rdh@genrad.com (Robert D. Houk)]

   >Sounds like a bug to me - the walls should be polished to a >mirror-like
   finish after the first thousand or so miles . . . >else the rings are not
   seated!

   Sorry to rain on your parade, BUT, The walls should always have the cross
   hatching on them otherwise the walls can't hold  an oil film that is needed
   for both lubrication AND ring sealling.

OK, so I should be more specific and careful in wording. When "new" (i.e.,
freshly "honed") the cylinder surface should have a texture roughly akin to
fine crocus cloth (very fine sandpaper/emorycloth) which is formed by op-
posing 45-degree-angle grinding of the surface, forming the "90-degree
crosshatch" you mention. As you slide your fingernail along the surface,
it is obviously "rough", with maybe the graininess of fine silk. Rings can
vary a lot in "new" condition, some have special "seating" coatings; etc.
and so forth.

When "seated", the rings should (have, in my experience) polished themselves
to a mirror-like surface, as if they were polished steel (which, basically,
they are). The cylinder surface, on the other hand, being "iron" (again,
typically, lotsa variations on the theme available; I'm not sure what the
"nitrided" (I think) iron surface looks like) will show its "grain" visibly.
This is somewhat different from the "crosshatching", but at a casual and
not-well-lit glance they're pretty much indistinguishable. To the touch
(run your fingernail along it, just like testing the edge of a knife), the
cylinder surface is again polished to a mirror-like consistency - you should
not be able to feel anything rough, other than surface dirt, carbon buildup
and ridge at top of cylinder, etc. If you shine a light carefully along the
surface, it should bounce off as if it were glassy-smooth (like glossy
photos versus matte-finished photos). If it is rough, you have a problem!

Microscopically, yeah, the surface is still rough (it's iron), which helps
trap oil. Macroscopically speaking, it's mirror-smooth, even if -- being
iron -- it makes a lousy mirror.

					-RDH