<VV> valve stem seals

Mark Durham 62vair at gmail.com
Wed Feb 10 12:18:26 EST 2010


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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