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<p>Current engine thinking is to move the wrist pin closer to the
top of the piston and to reduce the length of the piston (shorter
skirts) and zero quench (piston rises above the deck level). The
5th oil control ring served the purpose of (oil control) and also
to minimize piston slap on the cylinder wall as the piston
reversed direction leading to cylinder wall ovalization and
subsequent loss of compression. Dave<br>
</p>
<div class="moz-cite-prefix">On 4/18/2021 4:54 PM, Michael MacLean
via Healeys wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1959093511.3621729.1618786496615@mail.yahoo.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
I don't know about the six cylinder engines, but during the
rebuild of my BN2 engine I used 3 ring pistons from Moss. Not
exactly the most exclusive examples of piston technology, but the
very experienced engine builder that built my shot block for me
said they will do just fine. Heck I don't even remember seeing an
oil scraper ring on them. Not an expert, but could the way the
bottom ring was ground to shape have an oil scraping purpose?
<div id="yMail_cursorElementTracker_1618786399393">Mike MacLean </div>
<div id="yMail_cursorElementTracker_1618786421646">Out of my five
vehicles, only one has a catalytic converter. Take that Greta
Thunberg.<br>
<br>
<div id="ymail_android_signature"><a
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Android</a></div>
<br>
<blockquote style="margin: 0 0 20px 0;">
<div style="font-family:Roboto, sans-serif; color:#6D00F6;">
<div>On Sat, Apr 17, 2021 at 4:37 PM, William Atterbury via
Healeys</div>
<div><a class="moz-txt-link-rfc2396E" href="mailto:healeys@autox.team.net"><healeys@autox.team.net></a> wrote:</div>
</div>
<div style="padding: 10px 0 0 20px; margin: 10px 0 0 0;
border-left: 1px solid #6D00F6;">
<div id="yiv5269241550">
<div>
<div class="yiv5269241550ydpf5e37345yahoo-style-wrap"
style="font-family:Helvetica Neue, Helvetica, Arial,
sans-serif;font-size:16px;">
<div dir="ltr">
<div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Hey Ian,</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">The rumor I heard
was that the 5th ring was for hone-and-replace
rebuilds to reduce oil consumption. I'll let
others comment if these cars were fitted with 4
or 5 rings from the factory (I'm guessing 4). I
rebuilt mine with 4, like the others. Not a
problem for our coddled Healeys. Heck, I even
know of one fellow who only put in three for a
hot motor.</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Bill Atterbury</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">BT7</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">----------------------------------------------------------------------<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Message: 1<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Date: Fri, 16 Apr
2021 19:08:56 +0100<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">From: "Ian Hey"
<<a rel="nofollow noopener noreferrer"
ymailto="mailto:rianhey@btinternet.com"
target="_blank"
href="mailto:rianhey@btinternet.com"
style="color:rgb(25, 106,
212);text-decoration-line:underline;"
moz-do-not-send="true">rianhey@btinternet.com</a>><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">To: <<a
rel="nofollow noopener noreferrer"
ymailto="mailto:healeys@autox.team.net"
target="_blank"
href="mailto:healeys@autox.team.net"
style="color:rgb(25, 106,
212);text-decoration-line:underline;"
moz-do-not-send="true">healeys@autox.team.net</a>><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Subject:
[Healeys] To fit or not to fit<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:002201d732eb$915662a0$b40327e0$@btinternet.com"><002201d732eb$915662a0$b40327e0$@btinternet.com></a><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Content-Type:
text/plain; charset="us-ascii"<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">In a recent
engine rebuild of a standard BJ7 engine which
was fitted with<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">four ring
pistons, when I looked at replacement pistons
they were pictured<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">with five rings,
which did not seem good to me.<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">I fitted Omega
pistons from Denis Welch. These have three
rings with a<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">total width of
3.2mm compared with 9.8mm for the four rings.
(For the oil<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">rings only the
width contacting the cylinder bore is measured</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Since friction is
in proportion to ring width (possibly due to the
lower<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">pressure required
to make thinner rings seat against the cylinder
wall) this<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">represents a
reduction in losses to heat and a power increase
(small).<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Another, much
more expensive, option for consideration. I
also have no<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">doubts about the
quality of the pistons, whereas I am not sure
about the<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">four or five
ringed replacements. They seem very cheap to
me.<br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;"><br>
</div>
<div dir="ltr" style="font-family:Helvetica Neue,
Helvetica, Arial, sans-serif;">Ian</div>
</div>
<br>
</div>
</div>
</div>
</div>
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<pre class="moz-signature" cols="72">--
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