<VV> valve stem seals

[Daniel Monasterio]

Mark,

What a good an easy to understand lesson about valve train !!

Thanks 

Daniel

> Date: Wed, 10 Feb 2010 09:18:26 -0800
> From: 62vair at gmail.com
> To: frankcb at aol.com
> CC: chartzel at comcast.net; virtualvairs at corvair.org
> Subject: Re: <VV> valve stem seals
> 
> Frank, I overhauled my corvair heads back in 1967 at age 17, it was a 102 hp
> 62, and valve stem seals came with the gasket set and I did install them.
> That is why I said it might be splitting hairs when we talk about using them
> with normal valve guide to stem clearances, you need the seals to prevent
> too much oil from getting past and carboning up the valve. Those heads
> lasted 80K miles (when the nylon cam gear broke) and the valves were
> reuseable when I rebuilt them again. The engine was still running great when
> I sold the car another 80K miles later.
> 
> However, the technology used by the OTTO system has you lap the valve stems
> to the guide with much tighter clearances and due to the tighter clearances
> too much oil cannot get thru (but it does depend on the vacuum to provide
> enough to lubricate) and there is no need for, in fact if you use the seals,
> the valve will freeze up. They make the guides so you cannot install a stem
> seal on them.
> 
> So, if you are using std bronze or factory valve guides and are following
> the recommended clearances in the book (keep'em to the tight side), install
> the seals and don't worry about it. You should get satisfactory performance
> for many years.  However, if you want something better, install OTTO guides,
> the tuftrided valves, and use no seals. You'll get satisfactory performance
> for a longer period.
> 
> To keep it in perspective, If I were to drive 3K miles a year (so far I've
> averaged 1500), its 33+ years until I get 100K miles on the heads and since
> I'm 60 this year, I'm pretty sure I won't be driving the car that long.
> 
> If you really want to help out your valve train, do the std valve job then
> spend your money on roller rocker arms. The roller rocker arms stops the
> side loading that typically wears out the guides and makes the valves hit
> the seat off center! Also, with less side pressure strain on the rocker
> tips and valve stem tips, and rub pressure at the ball in the rocker, there
> is less strain on the cam lobes and lifters.
> 
> One of the reasons you can get 200-300K miles on engines today certainly is
> better machining, but it also has to do with the type of valve train
> geometry, the manufactuers redesinged the cams and rockers to a system that
> presses straight down on the valve stem with much less pressure on the cam
> and followers. That is why we need ZDDP in our oil and the modern engines
> don't.
> 
> Roller cams and roller rockers bring the antique corvair engine into this
> century technology wise, and if a modern computerized fuel injection and
> spark system was installed as well, the corvair engine would be just as
> durable and driveable. Mark Durham
> 
> On Tue, Feb 9, 2010 at 8:50 PM, FrankCB <frankcb at aol.com> wrote:
> 
> > Clark,
> > I agree for the EXHAUST valve guide.  But wouldn't there be a vacuum in the
> > cylinder for the INTAKE part of the cycle that could PULL oil uphill around
> > the INTAKE valve guide when the valve is off its seat and partly open???
> > Weren't stem seals provided by the factory on the stock Corvair engine??
> > Frank "wondering" Burkhard
> >
> > In a message dated 02/09/10 17:04:53 Eastern Standard Time,
> > chartzel at comcast.net writes:
> > On inline and V engines oil can run down the guides and cause smoky
> > starts until you burn off the oil.
> > On Corvair engines the guides actually run uphill so no oil is going run
> > "down" the guides.
> > There is no reason whatsoever to use stem seals on a Corvair.
> > Clark Hartzel
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