Engine cylinder bores are not lubricated ,as in "filled with oil under compression". The cross hatch is required to keep a microfilm of oil in place to lubricate the piston rings which have to tolerate high surface speeds and temps ranging from 80C to 900C on firing .[:)].I have some very old Mercedes blocks here with massive mileages on them and the cross hatch is still in place. Once an engine is allowed to run rich and the oil is washed off,the bores wear rapidly ,as do the rings. The glazed bore can no longer lube the rings and the engine begins to exhibit blowby and smoke. [xx(].A certain amount of initial wear is allowed to get the rings to match the surface of the bore and this will work for the life of the car as long as the engine is maintained .
With hydraulic cylinders running a synthetic type of seal, the idea of crosshatching doesn't provide a sealing surface but a means for fluid to escape under pressure .Via the scratches .
A tight seal will only seal as long as the seals surface against the cylinder wall is maintained. Eventually the edge of the scratches destroys the seal as it acts as a cutting edge. Admittedly this takes a period of time but as plenty of folks have found when honing brake cylinders it does happen before the bore shows signs of glazing again.
Modern Mercedes Engines with Nikasil bores are etched to provide the same surface with Acid after boring .
quote:
12-14-2004, 11:49 PM #8
Tom Hanson
MBCA Member
What the heck, try to stuff a MB 6.9 liter V8 in it. What a machine that would be..
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Tom Hanson
Orange County Section