Date: Sat, 28 Aug 2010 13:44:40 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Engine Assembly Wizzdom
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hi,
interesting.
where does one get the silk thread ?
in some ways an air-cooled opposed aluminum block aircraft engine is not
quite comparable to a liquid cooled opposed aluminum engine ...
different expansion factors in air-cooled versus liquid cooled.
I don't find case half leaks to be a common issue in waterboxer engines for
one thing.
I have put countless VW air-cooled case halves together with red Permatex
Hi-Tack gasket sealer ..
never a problem.
If there is a sealing problem on the case halves, I would expect it to be
because of physical imperfections ...warped case, dinged sealing surfaces,
just plan worn out, or rarely, not made correctly in the first place.
like it's not normally an issue in my experience.
of dozens , many dozens if wbxr engines that have come though my world in
the last whatever .....18 years...I think ONE had a case split oil leak.
One out of about 70 or more.
the silk thread thing ..
using that on a water-cooled wbxr engine ..I would regard that as an
experiment ..
and I am inclined to leave well enough along, and since wbxr case splits
don't leak for me,
I think trying something non-stock would be trying to fix a problem that
doesn't exist.
as in 'don't make things up' .
.....for sure, if there's a weakness from the factory ...absolutely ....come
up with a fix, ..we do that all the time in VW ...but there's no problem
with wbxr case half sealing that I know of.
some of the goofy stuff people come up with in Volkswagens is pretty
entertaining. Some of it is very valid and right on.
also...the air-cooled versus liquid cooled, and the different expansion
rates of the parts in those two types of engines ....it's a big factor and
should be thoroughly considered when trying to compare the two.
maybe silk thread expands at the same rate as aluminum or something. , lol.
AND ! ...............watch out for cheap modern silk thread - they don't
make it as good as they used to, most likely.
Scott
www.turbovans.com
----- Original Message -----
From: "Evan Mac Donald" <evanm@ATT.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, August 28, 2010 12:59 PM
Subject: Engine Assembly Wizzdom
I am plotting out the re-assembly of my 2.2 wbxer, and thought I would ask
about
a bit of Lycoming/Continental lore that I was recently exposed to.
For those who are unfamiliar with these engines, they are
horizontally-opposed,
air-cooled four cylinder engines, used to power many, if not MOST light
civilian
aircraft. Structurally, they are very similar to our versions of infernal
combustion units that power our VWs. Vertically-split on the center-line,
separate cylinder jugs, etc. They, and their maintenance, fall under the
purview
of the exceedingly conservative (mechanically) FAA.
When sealing the case halves together on these engines, two things are
used. Permatex Aviation sealant and silk thread. (Permatex is the only FAA
approved sealant.) But that's not my point. The interesting thing is that a
silk
(real silk, not polyester) thread is carefully laid down on one side of the
sealing surface, in the sealing compound, before the halves are fitted
together.
Does anyone know if this trick has been tried on any of the VW cases, and if
not, why not? There must be some advantage, my guess is in filling the small
crevices that machining processes leave, that the sealing compound alone
can't
cope with. The thread itself can't be thick enough to interfere with the fit
between the halves, can it? If this is an improvement for oil sealing, I am
all
in favor of it! It may just be there to keep the halves far enough apart for
the
Permatex to work properly, or maybe as a method to keep the halves from
"working" against each other at the seam.
Enquiring minds want to know...
