Re: Umbrella seals

[Curt Cleavinger <curt_cleavinger@domain.elided>]

Just to muddy the waters a bit more: I took the heads from my
Travelall's 392 to a machinist who does lots of IH stuff. He 
recommended Chrysler seals on (I think) the intake valves, and 
stock IH seals on the exhaust (the reason he doesn't use Chrysler 
seals on the exhaust valves is that the IH exhaust valve stems are 
an oddball size, while the intake are a common size. He also said 
that the exhaust side just isn't a problem - probably as Bill 
points out, the intake side is under vacuum, and would tend to 
suck the oil in, while the exhaust side is under pressure and would 
tend to blow the oil out). The Chrysler seals require a groove to 
be machined around the circumference of the valve guide boss. The 
seal is a  close, but not tight, fit over the valve stem - so it 
wipes the valve stem as the valve opens and closes. My engine still
has a puff of oil smoke at startup, but since the engine isn't 
broken in I'm not sure if this is due to valve seals or not.

Bill Thebert wrote:
> I don't recall which guides were which -- but I remember that the seals fit
> snugly over the guides on EITHER the intake guides OR the exhaust guides,
> but not both.  On the other, they were loose enough that the seal would
> "ride" up & down on the valve stem, rising up & down onto & off of the
> valve guide with each stroke.  On the snug-fitting guides, the seal
> remained firmly on the guide and the valve stem was "wiped" in both
> directions as the stem passed through.
> 
> I performed no machining of the valve guides; and I figured that either
> "mode of operation" provided more "shielding" of the stem-to-guide meeting
> point than the factory seals.
> 
> I apologize for the length here, John, for I know that you did not require
> the "recap".  I just wanted to assure that anyone who cared could follow
> along.
> 
> I'm curious whether your son noticed any "tendencies" regarding whether it
> was the intake or the exhaust guides that experienced accelerated wear in
> his view.
> 
> I'm also curious (possibly enough to remove a valve cover <g>)  which
> guides were the "tight fitting" ones and which were the "loose-fitting".
> 
> My hunch (and my first hypothesis) would be that the intakes were the
> tight-fitting ones -- which see the most benefit from the improved wiping,
> and which thereby do the most to prevent oil from being sucked in by engine
> vacuum.  I would further suspect that the exhaust guides (being subject to
> more heat) would be the first to fail from oil deprivation.  If these
> happen to be the "loose" ones, perhaps there's still enough splash to
> prevent their premature failure.
> 
> All speculation here, but curious nonetheless.

later,         curt_cleavinger@domain.elided  Louisville, CO
  Curt         Binder Bunch: http://www.off-road.com/~jweed/binder.htm
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