<VV> FW: PART II CERAMIC COATINGS MORE INFO

[Brandes, Guy]

Hi All more info on ceramics, I removed attachment on ring gap, if any
one wants info please contact me off line.
 
Regards,
 
Guy Brandes  65 VAIR 140
 
Hi Guy,
 
I am sorry to have forgotten to include some VERY Important information
about the ceramic modifications- and the unusual source for that
information.  I will admit that I didn't bother to calculate the new
compression ratio- on previous 140 engines I had always milled the step
out- even though the compression ratio was higher, the change in the
ratio between the 'squish' volume and the combustion volume actually
reduced octane requirements.
 
I did not perform this action on the wife's car because I felt that the
ceramics would reduce the octane requirements even more, and I didn't
want to introduce too many new variables.  
 
I had purchased a set of Keith Black pistons from Lon Wall at Corvair
Underground, and they came with a warning.  Because the pistons are
polished, they do not 'heat soak' as much as conventional pistons (and
consequently transfer that heat to the engine oil) the combustion
temperatures are higher.  The warning said that the gap on the TOP
compression ring MUST be enlarged, else the increased expansion of the
top ring from the higher temps would cause the ring to become heat
locked, causing a monstrous increase in ring to wall friction, and
likely major engine damage. 
 
I had had this happen on a previous motor, when the machine shop that I
had do a .060 overbore didn't bore the cylinders enough (apparently the
TRW book they used as a reference had the specs for a liquid cooled
engine, not the aircooled specs for Corvair, even though it said
'Corvair').  I had to replace the crankshaft on a new engine- not a
happy time.  Subsequent editions of the TRW book had the correct
figures- apparently word got out, but too late for me!
 
I realized that the change in combustion temps were likely to be
significantly greater with the coatings on both heads and pistons, so I
increased the gap over and above the figures provided by the Keith Black
folks.  I have included the tables from Keith Black as a .jpg
attachment- I don't know if you can include that on VV, but maybe you
can find a way.
 
The second compression ring is protected from the heat by the top ring,
so no further modification is needed.  
 
I hope this gets out before someone puts their motor together- I'd hate
to see my omission cause someone else such trouble.
 
Kirk
 
P.S. I opened up the ring gap by chucking the rings in a vise
(carefully! the rings are very brittle) slowly hand filing, taking great
care to keep the edges square, and often checking the gap by inserting
the ring into the cylinder bore.  I used the piston to push the ring
into the cylinder to be certain the ring was square in the bore.
 
P.P.S. I used stock head gaskets.

> Subject: FW: <VV> PART II CERAMIC COATINGS
> Date: Sat, 25 Oct 2008 06:31:57 -0500
> From: GBrandes at loebermotors.com
> To: kirkparro at hotmail.com
> 
> 
> 
> ________________________________
> 
> From: Western Canada CORSA [mailto:westerncanadacorsa at shaw.ca]
> Sent: Fri 10/24/2008 7:11 PM
> To: Brandes, Guy; virtualvairs at corvair.org
> Subject: RE: <VV> PART II CERAMIC COATINGS
> 
> 
> 
> Guy,
> 
> Is your friend able to provide an answer to this question?
> 
> Please thank him for everything he has provided so far as we're just
about
> to begin applying a ceramic coating on some engines we're building.
> 
> Regards,
> Joel
 
> 
> 
> What, if any adjustment did you do to take into account the thickness
of the
> paint when calculating the compression ratio? Did you go with a
thicker
> head gasket?
> 
> Regards,
> Joel
 
>