[Shotimes] Low pressure, high volume?

[John J. Weidenbenner]

Here's Clevite's web site for bearing construction info.

http://www.engineparts.com/products/

John W.

----- Original Message ----- 
From: "George Fourchy" <krazgeo@comcast.net>
To: <shotimes@autox.team.net>
Sent: Monday, August 23, 2004 1:42 AM
Subject: Re: [Shotimes] Low pressure, high volume?


> On Mon, 23 Aug 2004 01:13:27 EDT, Bobbonnit1@aol.com wrote:
>
> >I can't for the life of me, figure how rod bearings  would not get enough
> >lubrication for the short period of time that one would  "lug the
engine".
>
> It's not a short period of time.  Its a bit here, a bit there, and a bit
more here,
> there, and on and on for months or years.  Damage from lugging an engine
won't show
> up 'now' (back when it was a year or two old).....it shows up _later_
(now), when
> it's 14 or 15 years old.
>
> >You
> >would think that the upper end would run dry and you'll  ruin a cam
before
> >making a rod bearing spin. Before it spun, it would have to  run
completely dry
> >until friction grabbed it and pulled the little tab that  holds it in
place
> >completely flush!
>
> 1.  The cam and lifter oil supply comes off a separate oil gallery
(passsageway from
> the pump) than the main and rod bearings, and flow to it may or may not be
affected
> by low pressure or oil level.  2. You'd be surprised at the amount of
destructive
> energy in a connecting rod that is able to build up a little bit of
straight line
> inertia against the crank journal.....and again, the clearance required
for the
> damage to occur appears over a period of time.  A cam lobe is hardened, as
is the
> lifter or shim, so they are a little bit (a lot, actually) more durable
than the
> soft metal of a bearing shell and a crank journal.  And it doesn't need to
be
> completely dry....the single layer of lubricant molecules just has to fail
for a
> tiny micro-second.  Also, remember, when there is wear along an entire
bering shell,
> so that the shell's radius is a lot larger than the journal, the point
(and oil
> film) where the journal DOES come close to the bearing shell is under MUCH
more
> pressure than when radii are the same (when it was new).
>
> >What are OEM bearings made of  anyways?  Is being made of too
> >soft of an alloy cause premature failure in  early SHO's?  Are
replacements made
> >of a harder metal? What's the  difference (as far as rod bearings go) in
> >lugging the engine or turning over by  hand during assembly?  Why don't
they make
> >a high volume, high pressure  pump.......too much lube is a good thing
right?
>
> They are made of an aluminum shell with copper and lead alloys covering
the
> lubricating surfaces...very soft on purpose to protect the polished
journal...the
> oil does all the work.  There is no difference in bearings other than
improvements
> in surface metal alloys (for all practical purposes) found in any car
engine dating
> from the 40's-50's  to now.  They all do basically the same thing....the
oil is what
> has improved.  Not sure what you mean by turning over by hand during
assembly....one
> uses thick oil or assembly lube to put an engine together; also when a new
engine
> starts for the first time, wear does occur at a rapid rate....things are
just
> designed to allow that to happen, and when the wear is done, after
break-in, the
> clearances are what they need to be for long life.  Too much oil pressure
will lift
> the bearing out of its spot in the rod, disengaging (and allowing bending
of) the
> tang, and allowing the shell to spin much sooner in the engine's life, all
other
> variables inside the engine being the same.
>
> Wet sump oil lubrication systems are very finely designed.....you can't
second-guess
> design engineers (especially Yamaha engineers) this easily.  In my
> experience....playing hard with engines since the '60s...no one group of
folks has
> asked their cars' engines to last as long as these are without attention,
and the
> original engineers didn't think they would.  It's our 'fault', and we have
to make
> the allowances.  Be easy on them, or rebuild them.....take your choice.
>
> George
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