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Hi Rafael,
I don't think the piston in your picture is an original Austin piston. I
have never seen an original piston with the "slipper" shape or one with the
groves on the body that yours has consequently, the ring package is not
what would normally be used.
The top ring is indeed a compression ring but the others are all what we
used to call "cord" rings and are I believe designed for oil control not
compression. I'm pretty sure that all original pistons had 2 compression
rings.
That said however there is no good reason why they should not work.
Although the picture is not very clear it would also appear that the piston
is slightly "domed". I'm pretty sure that the original pistons in a
tri-carb were flat top so I would strongly recommend that you check the
actual compression ratio to ensure that the engine has not been modified so
much that it will not run well on pump fuel.
I'm sure that your machine shop knows what they are doing but the cylinders
should not be "polished" but honed before reassembly.
Hope that helps.
Michael S
BN1 #174
http://www.netbug.net/blogmichael/?p=3D445
On Thu, Jan 8, 2015 at 8:43 PM, Rafael Abugattas <rafaelabugattas@yahoo.es>
wrote:
> Hi all,
>
> I just started a nut and bolt restoration on my 1962 BT7 Tri Carb. Today
> we took the engine apart and sent the block and head to the machine shop.
> On a first inspection, it seems that the cylinders do not need to be bore=
d,
> only polished.
>
>
>
> My mechanic is concerned about the pistons and the type of rings it uses.
> Enclosed is a picture of one of the pistons and the three set of rings.
>
>
>
> I am no expert but according to his explanation: Starting from the right,
> the first thick ring on the picture is the compression ring. The middle o=
r
> second set includes two additional thin compression rings and what seems
> like an heptagon that I understand helps keep the rings open. The third s=
et
> includes three lubrication rings.
>
>
>
> He mentioned that the middle set of two thin compression rings with the
> heptagon is not a very common configuration. He was wondering whether the=
y
> could be substituted with one regular compression ring.
>
>
>
> He has worked before on a Healey engine and he doesn=C2=B4t recall piston=
s with
> the grooves on the side like the one on the picture. I guess the groove
> design helps with the lubrication and cooling of the pistons. Are these
> original pistons? Would you recommend changing them?
>
>
>
> Thanks in advance for your comments.
>
>
>
> Best regards,
>
> Rafael
>
>
>
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--=20
*If you can't fix it with a hammer, you've got an electrical problem.*
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<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-family:comic sa=
ns ms,sans-serif;font-size:small">Hi Rafael,<br></div><div class=3D"gmail_d=
efault" style=3D"font-family:comic sans ms,sans-serif;font-size:small">I do=
n't think the piston in your picture is an original Austin piston. I ha=
ve never seen an original piston with the "slipper" shape or one =
with the groves on the body that yours has consequently, the ring package i=
s not what would normally be used.<br><div class=3D"gmail_default" style=3D=
"font-family:comic sans ms,sans-serif;font-size:small">The top ring is inde=
ed a compression ring but the others are all what we used to call "cor=
d" rings and are I believe designed for oil control not compression. I=
'm pretty sure that all original pistons had 2 compression rings.<br></=
div><div class=3D"gmail_default" style=3D"font-family:comic sans ms,sans-se=
rif;font-size:small"></div></div><div class=3D"gmail_default" style=3D"font=
-family:comic sans ms,sans-serif;font-size:small">That said however there i=
s no good reason why they should not work. <br></div><div class=3D"gmail_de=
fault" style=3D"font-family:comic sans ms,sans-serif;font-size:small">Altho=
ugh the picture is not very clear it would also appear that the piston is s=
lightly "domed". I'm pretty sure that the original pistons in=
a tri-carb were flat top so I would strongly recommend that you check the =
actual compression ratio to ensure that the engine has not been modified so=
much that it will not run well on pump fuel.<br></div><div class=3D"gmail_=
default" style=3D"font-family:comic sans ms,sans-serif;font-size:small">I&#=
39;m sure that your machine shop knows what they are doing but the cylinder=
s should not be "polished" but honed before reassembly.<br></div>=
<div class=3D"gmail_default" style=3D"font-family:comic sans ms,sans-serif;=
font-size:small">Hope that helps.<br><br></div><div class=3D"gmail_default"=
style=3D"font-family:comic sans ms,sans-serif;font-size:small">Michael S<b=
r></div><div class=3D"gmail_default" style=3D"font-family:comic sans ms,san=
s-serif;font-size:small">BN1 #174<br><a href=3D"http://www.netbug.net/blogm=
ichael/?p=3D445">http://www.netbug.net/blogmichael/?p=3D445</a><br></div></=
div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Thu, Jan 8=
, 2015 at 8:43 PM, Rafael Abugattas <span dir=3D"ltr"><<a href=3D"mailto=
:rafaelabugattas@yahoo.es" target=3D"_blank">rafaelabugattas@yahoo.es</a>&g=
t;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0=
.8ex;border-left:1px #ccc solid;padding-left:1ex"><div link=3D"#0563C1" vl=
ink=3D"#954F72" lang=3D"ES-PE"><div><p class=3D"MsoNormal"><span lang=3D"EN=
-US">Hi all,<u></u><u></u></span></p><p class=3D"MsoNormal"><span lang=3D"E=
N-US">I just started a nut and bolt restoration on my 1962 BT7 Tri Carb. To=
day we took the engine apart and sent the block and head to the machine sho=
p. On a first inspection, it seems that the cylinders do not need to be bor=
ed, only polished.<u></u><u></u></span></p><p class=3D"MsoNormal"><span lan=
g=3D"EN-US"><u></u>=C2=A0<u></u></span></p><p class=3D"MsoNormal"><span lan=
g=3D"EN-US">My mechanic is concerned about the pistons and the type of ring=
s it uses. Enclosed is a picture of one of the pistons and the three set of=
rings. <u></u><u></u></span></p><p class=3D"MsoNormal"><span lang=3D"EN-US=
"><u></u>=C2=A0<u></u></span></p><p class=3D"MsoNormal"><span lang=3D"EN-US=
">I am no expert but according to his explanation: Starting from the right,=
=C2=A0 the first thick ring on the picture is the compression ring. The mid=
dle or second set includes two additional thin compression rings and what s=
eems like an heptagon that I understand helps keep the rings open. The thir=
d set includes three lubrication rings.=C2=A0 <u></u><u></u></span></p><p c=
lass=3D"MsoNormal"><span lang=3D"EN-US"><u></u>=C2=A0<u></u></span></p><p c=
lass=3D"MsoNormal"><span lang=3D"EN-US">He mentioned that the middle set of=
two thin compression rings with the heptagon is not a very common configur=
ation. He was wondering whether they could be substituted with one regular =
compression ring. <u></u><u></u></span></p><p class=3D"MsoNormal"><span lan=
g=3D"EN-US"><u></u>=C2=A0<u></u></span></p><p class=3D"MsoNormal"><span lan=
g=3D"EN-US">He has worked before on a Healey engine and he doesn=C2=B4t rec=
all pistons with the grooves on the side like the one on the picture. I gue=
ss the groove design helps with the lubrication and cooling of the pistons.=
Are these original pistons? Would you recommend changing them?<u></u><u></=
u></span></p><p class=3D"MsoNormal"><span lang=3D"EN-US"><u></u>=C2=A0<u></=
u></span></p><p class=3D"MsoNormal"><span lang=3D"EN-US">Thanks in advance =
for your comments.<u></u><u></u></span></p><p class=3D"MsoNormal"><span lan=
g=3D"EN-US"><u></u>=C2=A0<u></u></span></p><p class=3D"MsoNormal"><span lan=
g=3D"EN-US">Best regards,<u></u><u></u></span></p><p class=3D"MsoNormal"><s=
pan lang=3D"EN-US">Rafael<u></u><u></u></span></p><p class=3D"MsoNormal"><s=
pan lang=3D"EN-US"><u></u>=C2=A0<u></u></span></p></div></div><br>_________=
______________________________________<br>
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<br></blockquote></div><br><br clear=3D"all"><br>-- <br><div class=3D"gmail=
_signature"><div dir=3D"ltr"><div><div dir=3D"ltr"><i><font><span style=3D"=
color:black">If you can't fix it with a hammer, you've got an elect=
rical problem.</span></font></i><br><br><div></div><div></div><div></div></=
div></div></div></div>
</div>
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