<VV> Plateau honing

[John Dozsa]

> Date: Wed, 30 Mar 2005 01:38:47 EST
> From: BobHelt at aol.com
> Subject: <VV>  Plateau honing
SNIP
> 
> Plateau Honing
> 
> Cylinders, after boring, must be honed to set the exact cylinder dimensions
> and roundness. In addition the wall roughness must be very closely controlled.
> The honing operation should make the walls relatively smooth for little wear
> but also rough for oil retention. Previous practice was to use fairly rough
> stones to leave a fairly rough rough wall surface...like 220 or 280 grit stones.
> This would leave the oil retention grooves and the rings were expected to
> smooth out the surface during the breakin period.
> 
> The problem was that the rings were used to wear in the cylinder surface.
> This was undesirable for several reasons. It took many miles to get the rings to
> seat. The engines didn't develop full power until the rings seated. The engine
> may use oil until the rings seat. The engine didn't meet emissions
> requirements until the rings seated (for example, pity the poor customer who has his
> engine rebuilt and shortly thereafter is required to pass his state's smog test!)
> Another, maybe worse, problem was that the rings were wearing in the cylinder
> surface and releasing "tons" of small metal particles into the oil which
> could cause much damage elsewhere before they were removed by the filter (if they
> are ever removed. That's another subject for discussion.).
> 
> So the industry got smart, finally, What was required were two separate
> honings. The first was a rough hone to establish the wall dimensions and oil
> retention grooving. The second honing operation was with very fine stones (or
> brushes) to remove just the smallest amount of material, but to smooth the cylinder
> walls. Just as the rings would do during breakin. This is called plateau
> honing since a microscopic cross-section view of the cyl wall would show jagged
> valleys but with the top peaks all smoothed off like a plateau. Sort of like
> taking a mountain range and cutting off all the peaks to some level. All the new
> cars use this plateau honing technique and a few engine rebuilders do too.
> 
> I hope that this helps.
> Regards,
> Bob Helt

Questions ...........

1. Are the cylinder barrels sold by Corvair vendors plateau honed?

2. If no, would you go out of your way or pay more for plateau honing
vs. the wear in break-in oil technique?

3. Do plateau honed engines last longer than non plateau honed engines? 
Obviously keeping all maintenance equal.

John Dozsa