Tom, here's my answer to the break-in lube question.
First half (to pass the filter)--
Certain load carrying wear surfaces in an engine cannot be machined
perfectly enough to allow development of a perfect high pressure load
carrying oil film. They need to form that perfect geometry after assembly
and under running conditions of temperature, loads, deflections, etc.
Examples of this are crankshaft and cam bearings, piston skirts, and to a
much lesser extent most of the other wearing surfaces of an engine. In
these components as the surfaces literally wear to a "perfect" fit a good
fluid film pressure distribution is able to form in the "bearing" and the
clearances are enough top keep the metal surfaces from touching as well as
lubricant to flow to carry away any heat developed by the shearing movement
of the lube oil.
The exceptions to this case, at least with respect to heavily loaded parts
in the engine, are in the piston rings and to a lesser extent other places
where high pressure liquids or compressed gasses have to be prevented from
leaking (oil and water pump seals for example). With these mechanical
devices the typical clearances on the order of a thousanth of an inch more
or less would allow way too much leakage. So they want to run with their
surfaces touching to the point of being under continuous wear. In the world
of bearing engineers this is called mixed film lubrication and in the
extreme boundary lubrication. Really important here are the material
combinations that have evolved over 200 years of machinery development.
Ed Weldon
----- Original Message -----
From: "Tom Neimeyer" <Tneimeyer@houston.rr.com>
To: "Ed Weldon" <23.weldon@comcast.net>; <land-speed@autox.team.net>
Sent: Friday, October 20, 2006 5:39 PM
Subject: Re: Engine Assembly Lube
> One question, I have heard some say "never use synthetic for break in" and
> others say it's OK, what are the lists thoughts?
> Cheers, Tom
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