I guess I don't get all of the FOT messages through AOL, so I don't know the
entire conversation but with the 87mm bore and much more than .075 or so off of
the head, you're gonna start to lose that shroud (good).
Once the shroud is gone, the old steel "shim" gasket is the only one I use, it
works fine.
It requires good studs/nuts, good surfaces, liner top relief around the inlet,
and correct liner protrusion, to work reliably.
I have no experience with "big" bore engines but at least you probably don't
have to do the inlet valve relief in the liner.
Glen
-----Original Message-----
From: Jerry Van Vlack via Fot <fot at autox.team.net>
To: asg123 <asg123 at centurylink.net>; triumphs <triumphs at autox.team.net>
Cc: 'Friends of Triumph' <fot at autox.team.net>
Sent: Wed, Sep 20, 2017 7:19 pm
Subject: Re: [Fot] [TR] TR4A head gasket, 87 mm cylinders
I?m interested in the responses too as I recently suffered a head gasket
failure around the intake shroud of #4 using a 91 mm Cometic (very similar to
the Lucas new improved one) In my case the head is milled .090 using 87 mm
liners. The old Payen style lasted 30 or more years until I did a valve job 4
years ago. The Cometic lasted 4 years until it failed. I?ve discovered some
extenuating circumstances which may have caused my failure but I am interested
in the responses, especially from those who have moved up to the 89 mm liners.
How have you sealed the 89?s and or is it too early to report results? Also
please indicate if you?ve milled the head and by how much.
I?ve discussed this with some very reputable Triumph performance folks in the
last week and gotten some good input but would like to broaden the discussion.
Once we see some responses I?ll be pleased to share what I?ve discovered. Those
who I?ve already discussed this with can chime in or not, I will include your
advice but not who you are unless I have your permission. But I?d like to hear
some input from others before I do that.
Regards,
Jerry Van Vlack aka JVV
66 TR4A
From: asg123 at centurylink.net
Sent: Wednesday, September 20, 2017 1:51 PM
To: triumphs at autox.team.net
Subject: [TR] TR4A head gasket, 87 mm cylinders
I have asked a similar question before but my mechanic and I are still
undecided which rabbit hole to enter
Does anyone have experience with which head gaskets hold up best against
blowing out around the combustion chambers? I see the stainless steel
composite gaskets which claim to be the best. But, some people, including the
tech support at BPNW, say that the OE copper gasket by Payen withstands high
compression the best. How does the German made Payen copper gasket hold up
compared to the Lucas OE type copper gasket? We had an OE copper head gasket
blow out between cylinders #1 and #2 after only a few thousand miles. It was
using 93 octane gas with the timing retarded a couple degrees to keep down
spark knock, but it still dieseled on when we tried to shut it off. A solid
copper head gasket from Gasket Works custom milled to drop the compression to
130psi fixed the spark knock and dieseling, but we had chronic problems with
the oil and water weeping into each other no matter what sealants we tried. As
always thanks for your responses. Arnold
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