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Re: Bearing theory

To: "John Kipping" <johnkipping@inet.net.nz>, <Gt6steve@aol.com>,
Subject: Re: Bearing theory
From: "kas kastner" <kaskas@cox.net>
Date: Wed, 5 May 2004 16:56:25 -0700
  You have made an interesting comment on the smaller bearing surfaces.  The
Ford GT-40 I understand when first produced, was introduced with a new
engine that had an improved crankshaft  It was a larger main bearing size.
It sapped the power.  The surface speed is up and the power is down. They
went back to the old engine. Jimmy Coan did tests with the help of the
Barkers to test the big bearing and the small bearing cranks.  The small
bearing cranks were about 5 horsepower clear of the big bearing. Knowing
this I also conjectured the thoughts of the six cylinder engines with
smaller journals. The GT-6 maybe, but the TR-6 does not have any overlap
already  so I doubt that is the ticket for long life,  but with the GT-6 ,
maybe. By the way on the MK-4 Spitfire they did change the block to clear
the new rods that were common to all the engines and this is called the
"power bulge".HAH!!!!!
  ----- Original Message ----- 
  From: "John Kipping" <johnkipping@inet.net.nz>
  To: <Gt6steve@aol.com>; <FOT@autox.team.net>
  Sent: Wednesday, May 05, 2004 3:29 PM
  Subject: Re: Bearing theory


  > An interesting fact - there are two versions of 1300 engine, the Mk III
  > Spitfire one with small bearings, and the Mk IV one with large bearings
  > (commonised ones from TR5 and 6). Not only do the large bearing version
  > engines not produce the same power as the small bearing ones - they also
  > have a much shorter bearing life. (Uk versions are better because apart
from
  > crank bearing size the engines are identical). The only factor in the
  > shorter life must be that the speed across the bearing is higher with a
  > bigger diameter - think what a six cylinder would be like with smaller
  > bearings.
  > John Kipping
  > ----- Original Message -----
  > From: <Gt6steve@aol.com>
  > To: <FOT@autox.team.net>
  > Sent: Wednesday, May 05, 2004 2:25 PM
  > Subject: Bearing theory
  >
  >
  > > Amici,
  > >  All this bearing talk of late has me exploring the empty caverns of
my
  > mind.
  > >  While pondering the quoted PSI ratings for the King bearings I
realize I
  > > have no idea what my engine requires.  It seems there's a factor
missing
  > from the
  > > equation.  I know surface area of the piston but what the hell is a
  > > reasonable figure for the combustion pressure applied to the bearing.
  > Surely it's not
  > > directly proportional to CR.  Or is it?  Is there a general value
  > accepted?
  > > What if my killer head burns better than the stock one?  Higher
pressures
  > > applied to the bearing obviously so without knowing your exact
Volumetric
  > > Efficiency and the pressure produced in the chamber how can we guess a
  > suitable
  > > bearing?  Disregarding all the shiny bits in the filter.
  > > Then, how does the surface speed of the bearing factor in??  Would a
ten
  > > percent reduction in surface speed (or one or twenty) be more
significant
  > to the
  > > bearing life?
  > > Enquiring minds want to know...Steve

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