WARNING - Valve Stem Seals

[jlandry@domain.elided (John A. Landry)]

Reapers,

I took time this afternoon to call Dana Corp's Perfect Circle Div. to
discuss the valve stem seal situation with them.  I spoke with Walt Dehaven
who is their Product Specialist on valve products.  Here's what I found
out...

Regarding the correct application of Perfect Circle seals for the V392
engine, it turns out Dana's catalog IS WRONG!  Walt thinks it probably has
been wrong for 20+ years!  Dana's catalog called out part number VS-12 a
set of 16 rubber / teflon seals to fit *both* the intake and exhaust valve
stems.  Anyone who knows anything about the V392 knows that the exhaust and
intake stems diameters are different sizes.  The intake valve features a
common 3/8" diameter stem, while the exhaust valve measures some oddball
diameter of .414"... which doesn't equate to any standardized size... not
even metric.

What's funny is that Dana's own records show the V392 takes two different
sized valve guides, which they also sell.  Yet for the seals, somehow their
prints are in error and they showed using a seal (Dana part number 1812)
designed to fit a 3/8" stem for both valves.  Walt confirmed you SHOULD NOT
attempt to use the 3/8" seal on the larger exhaust valve stem.  The reason
is that the seals are specifically engineered to allow a small metered
amount of oil past the Teflon insert to lubricate the upper portion of the
valve guide.  If the seal were stretched over the exhaust valve, the
metering properties would be eliminated and likely the seal would be
destroyed (pulled apart) due to the high degree of friction between it and
the valve stem.

On the bright side, Walt told me that generally only the intake needs a
full seal and the exhaust valve stem only needs a deflector type seal.
Walt claims to have been building racing engines for 34 years, so I suppose
he knows what he's talking about.  The original o-ring seal I used is what
termed a deflector style seal and is adequate for the exhaust.  The o-ring
seal is there to keep oil pooled up in the valve spring retainer and
prevent it from trickling down straight into the valve guide.  Since the
intake is under constant negative pressure, a full seal is more beneficial
to eliminate the chronic IH puff-of-oil at startup.

As it turns out, Dana does not have a full wipe type seal to properly fit
the exhaust stem of the V392, so very likely future editions of their
catalog will eliminate the listing for that engine altogether.  The VS-12
seal set is still a proper fit for the 304 and 345.  It can also be used
for the 196 and the intake stems only on the 392.  You'd have a 8 seals
left over for the 196 and the V392.

The corresponding valve guide cutter required to install the Perfect Circle
guides is Dana part number VST-1812, and it's also designed only for a 3/8"
ID valve guide.

Since I already ordered a set of seals from NAPA, I'm going to go ahead and
install them on the intake guides of my V392 and just stick with the
original o-rings on the exhaust valves.

Regards,

John L.
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