<VV> 140 Valve Seats

[Ron F Hinz]

You're totally neglecting what may be the biggest factor and that is the
smaller coolant passages on the 140 heads due to it's larger valves which
cuts the air flow.  Of course it will have problems as the cooling is
already marginal with the standard valve heads!
RonH

----- Original Message ----- 
From: <RoboMan91324@aol.com>
To: <virtualvairs@corvair.org>; <dmacd_us@yahoo.com>
Sent: Wednesday, June 09, 2004 11:09 AM
Subject: <VV> 140 Valve Seats


> Hello David,
>
> While I agree that running an engine at its limits will shorten its life
when
> compared to one run gently, I respectfully disagree with your position on
the
> 140s.  There are a number of reasons that the 140s drop seats more than
> others but by far, the main reason is purely technical and the driving
habits of a
> 140 owner are secondary.  The 140 HP engine has larger diameter valves and
> valve seats.  When things get hot, the aluminum head expands more than the
steel
> valve seats and the interference fit between them lessens.  This is when
the
> seat tends to drop.  All Corvair engines suffer from this malady to
different
> extents but the 140 is still worse than even the turbos which I suspect
would
> also be driven hard.  While in boost, the turbos tend to run much higher
> temperatures than even the 140s but don't have the dropped seat problem as
bad as
> the 140s.  This is specifically due to the larger diameter seats.  I could
go
> into details of the thermal coefficient of expansion of aluminum vs. steel
but
> don't want to put you to sleep.
>
> Doc
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In a message dated 06/09/04 7:10:17 AM Pacific Daylight Time,
> virtualvairs-request@corvair.org writes:
>
> > Message: 1
> > Date: Wed, 9 Jun 2004 05:47:27 -0700 (PDT)
> > From: Macdonald David <dmacd_us@yahoo.com>
> > Subject: Re: <VV> 140 Valve Seats
> > To: virtualvairs@corvair.org
> >
> > My theory is that 140's drop valve seats becuase they are 140's and
people
> > buy them becuase they can drive them hard and do just that.
> >
> > If non-140's spent as much time at WOT they would drop almost as many
seats
> > :)
> >
> > My theory is based almost no data whatsoever, so I don't think it's
> > statistically valid either.
> >
> > [When I was still a teenager, I owned a '68 GTO. I went through three
> > engines in that car. My conclusion at the time was that Pontiac 400's
were
> > unreliable. I have teenagers of my own now so I know the engines were
fine, it's
> > teenagers that are the problem]
> >
> > David
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