At the Engine Room we have always used chromed top compression rings and
have had no problem getting them to seat. We hone the cylinders with a
"Brush Hone" with the little abrasive balls on flexible plastic stalks. We
use the appropriate grit for chrome rings, I believe it is 280 or so and
then wipe the cylinders with atf and a white paper towel until there is no
more grey color comming off onto the paper towel. The rings seat in 20
minutes of running. the ring manufacturers say the the rings are "lapped in"
to a cylinder of the correct bore during the manufacturing process and so
are actually "pre broken in".
The main advantage of "ductile iron" top rings is that they are very
resistent of breakage caused by detonation. Sealed power, now owner by
Federal Mogul Corp. used to make 1/16" ductile iron chrome plated riings in
87mm, but have not done so for a number of years. I have looked into having
them made, but they want a min. order of 1000 rings or so. The rings are
available in metric widths and an 87 mm bore so it is possible to have
custom pistons made the will accept these rings.
The only "seating " problems we have had, and they have occured enough
times to have been a real problem, is with the cast oil rings not seating
and the engines burning oil and smoking out the exhaust. We no longer will
build an engine using the cast, 1 piece oil control rings that come on the
"Hepolite Powermax" pistons. We replace the oil rings only with modern,
American 3 piece oil control rings, and have never had an oil consumption or
smoking problem siince. We normally us either sealed power rings, which we
buy in separate pieces and make up for the specific application based on
race or road use, or we use offf the self Hastings oil control rings.
We ahve never used any "gapless " rings of any sort. With the proper end
gap, about .013" top ring on an 87mm bore, and around 12:1 or higher
compression ratio with a 300 degree raciing cam, we get cranking compression
figures of around 240 psi and cylinder leakage of about 4-6 %. when the
engine is hot.
The sealed power ring engineers say that it is very important the there
be a high differential pressure between the area above the top ring and the
area below the top ring. It is this pressure that presses the ring out
against the cylinder wall and down against the 2'nd ring land of the piston.
With a gapless 2'nd ring, the 2'nd ring seals to well and causes the
pressures above and below the top ring to be more nearly equal and this
actually degrades the seal of the top ring to the piston and cylinder wall.
According to those engineers that I have talked to, the primary purpose of
the 2'nd ring is oil control and not cylinder pressure sealing.
Regards, Greg Solow
----- Original Message -----
From: Jack Brooks <brooks@belcotech.com>
To: Friends of Triumph <fot@autox.team.net>
Sent: Wednesday, June 20, 2001 2:12 PM
Subject: Rings
> Since we talking rings......
>
> When I brought my engine components into my machinist, he was all over my
case
> about not using ductile rings. He pulled some old ones out of a bin and
could
> twist them up without them breaking. Since I knew the Deves rings I had
were
> good ones, but certainly not ductile like those that he had, and my second
> compression ring was already made gap-less by Total Seal, I passed on
> acquiring a set of the ductile ones. I've always wondered about those
rings.
> Anybody ever use a set in a Triumph or other engine?
>
> What are the advantages and/or disadvantages?
>
> Thanks,
>
> Jack Brooks
>
>
> BTW - the machinist was a cantankerous old bastard, who loved to argue
about
> anything, but he did a great job. He was not really familiar with LBCs,
but
> he built race engines (road, drag and marine) on a regular basis and had a
> bunch of very happy clients wander in checking on their work on that
Saturday
> morning I "interviewed" him. He loved reading Kas's Competition book too,
so
> I knew he wasn't all bad. <Grin> I loaded it to him for things like rod
> lightening, etc.
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