Re: Mono liners was Monosleeve liners & / or Monoblock liners

[bearbvd@domain.elided (Greg Hermann)]

At 6:56 PM 10/26/01, AlfaCyberSite wrote:
>Greg, yours is the first reply I've received regarding the mono liners.
>So, in
>lay persons terms, what is Bore Tech hardening? And, I agree with your
concern
>regarding trannies / diffslet alone the rubber donut issue.
>
>Since you're an engineer and should one allow one's mind to flow freely,
what
>about a pressure-cast aluminum block with cast-in silicon-aluminum cylinder
>sleeves? Unless one greatly beefs up (redesigns) the basic Alfa block, it
>seems to me the old original block with mono liners would be as strong,
>if not
>stronger.

Yep, see detailed comments below. The deck plate is the real key.
>
>Is there really a problem with the oil pressure to the cam follower
bores?Or
>do you feel it Might become a problem should major HP be extracted from
>the 2
>liter engine?
>
>Comments?
>
>Biba
>
>*********

There is an outfit in Ohio (I don't remember the name of the town offhand),
named Bore Tech. Lots of motorcycle guys, particularly Harley folks, use
it. One POLISHES the cylinder bores to about a 4 to 8 micro-inch finish
(rather than the usual cross-hatched hone pattern) at the final size, and
then sends the liners/barrels/block to BoreTech. It is a proprietary
treatment that yields a _very_ hard (about Rockwell C-70) surface hardened
finish on the bores. Some sort of a carbide conversion, I _think_ (???).

This bore hardening process is purported to increase wear life by a factor
of three to six. It is probably similar to the "Nikasil" thing that Porsche
and others used to do.

It is, however, hard enough so that lapping the rings to pre-seat them
prior to assembly is a good idea. This can be done with a spare
liner--probably best to have one hardened by Bore Tech after finishing to
the same diameter as the ones to be used, but honed a bit deeper, so that
it is not fully polished out--some remaining hone marks, such as one might
find on a liner with 10K or so miles on it. (The hone marks give the
lapping compound a place to reside whilst fitting the rings.)

A pretty simple matter so make up a dummy "piston" out of a stray chunk of
aluminium so as to hold the rings (one at a time) for lapping them in the
stray liner turned "lap".  1 micron diamond lapping compound is probably
the best choice for this job. Chrome faced rings are likely the best (only
??) choice for use with such a  hard a bore surface. I tend to like
chrome/ductile, barrel faced top rings, Total-Seal seconds, and the "H"
shaped, coil spring expanded, type oil rings, preferably with chrome on the
bore contact surfaces (this type of oil ring was used in lots of Porsche
flat sixes).

As for pistons, I tend to lean toward 4032 alloy forgings--4032 is the
moderately high (but hypo eutectic) forging alloy with low expansion
characteristics. Virtually equal to 2618 in strength, but not as ductile.

I am also partial to the idea of a teflon impregnated hard anodized coating
on the pistons, such as is done by Nimet Industries (Gary, IN). Again--this
coating has a surface hardness in the R C-70 neighborhood. It is not only
extremely low friction, it is very long wearing, and precludes _any_
tendency for the pistons to gall.

I would suspect that 4032 forged pistons with the described coating could
be successfully run with a bore clearance of .001" to .0015" (Clearance
WITH the coating in place, see below).

I even believe in using this coating IN the ring grooves. Most high
performance Alfa engines I have been around have a serious problem with
wear in the ring grooves (in a vertical direction). I believe this coating
would cure it about as well as the cast in duriron top ring insert does in
HD truck and diesel pistons !

The Nimet coating is generally .002" thick, with .001" of penetration and
.001" of "build", so one would likely have to devise a holder for the rings
so that they could be sanded .0015" to .002" thinner than stock on a
surface plate. (I REALLY am not interested in asking some poor piston mfgr.
to make up pistons with .002" wider than normal ring grooves, I can just
HEAT the squalling that would result !!!)

And, yes, I do believe in using one of the ceramic heat barrier coatings on
the piston crowns.

As regards the block-- yes, a pressure (or die) casting is slightly denser,
and therefore marginally stronger than a sand cast part, but the very
nature of the die design (one must be able to remove the part from the
die!) puts limitations on the shape of the casting which I believe more
than makes up for the strength difference vs. a well designed sand casting,
such as the Alfa block is.

I think the REAL potential for increasing the strength of an aluminium
block lies in using one piece for all of the bearing caps which also
fastens to the pan rails (such as was first (??) done in the Ford/Cosworth
DFV FI engines,  as well as in several subsequent designs.

I also think there would be a lot of potential improvement by using
"through" studs--lay the block out so that the main bearing cap studs were
extensions of the cylinder head studs.

As for oil to the cam follower bores, I am not sure. Just a thought that I
have had floating around for a number of years.  The more aggressive the
cam, the more important it would become, though. Always did like the Jag 6
approach of pressing an iron insert into the follower bores--- . The thing
that really fostered the idea for pressure oil there was that I had a
design/patent disclosure floating around (since about '69)  for a
hydraulically adjusted bucket type cam follower. This was _LONG_  before
emissions requirements drove the Japs to develop just such a thing!

Talk about having a decent idea _way_ too soon !!! :-)

As far as using turbos goes, proper selection is _everything_ !!!  In a
good, well selected and well tuned installation, the boost gauge will
pretty much follow the throttle pedal !! I am also a firm believer in VATN
(Variable Area Turbine Nozzle) turbo technology. The low end torque and
response that can be achieved with these far exceeds even what can be done
with good, well matched positive displacement superchargers! Try a peek at
<www.aerocharger.com> for a start if you are curious. Full boost by 1500 or
2000 rpm is well within the capabilities of these units.

It would be real fun to build up an Alfa 4 using all of the above discussed
technology. Probably use some of the "Weber pattern" throttle bodies,
complete with injector bungs --TWM (??)--or some such. To me the REAL trick
here would be to use some form of air shrouded injectors so as to retain
the wonderful fuel atomization quality (and resulting responsiveness)  that
Webers give----- .

I think there are some late model Bimmers that use a Bosch air shrouded
port injector, and I sort of assume that the new Bosch direct injectors
which I have seen advertised occasionally MUST use (compressed) air to do
their thing.

Shouldn't be too much of a trick to mount a small air compressor on a Spica
front cover----

Regards, Greg

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