<VV> 140 Valve Seats

[RoboMan91324@aol.com]

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