I called ARP. They say (contrary to some other sources I looked at) always
re-torque a cold engine, not hot. The advice was to back off the nuts and
re-torque one at a time, same pattern as when the head is first installed. The
reason for backing off first is that the in-place ?break-away torque? may be
higher than the desired torque setting, i.e., there?s friction from breaking
loose a static connection that may exceed the original torque setting. Trying
to tighten from the as-is position may give a false reading that?s higher than
the desired torque setting.
I asked about re-lubing - the indication was that?s probably not necessary,
unless you are dealing with an engine that has been sitting a long time or run
many hours and had the original lube bake off, and that?s not likely to be the
situation when we are all re-torquing the head.
Thanks for all the feedback!
Scott
On Sep 20, 2017, at 6:46 AM, barry rosenberg via Fot <fot at autox.team.net>
wrote:
Contact Mr. Gasket. They make the Payen gaskets and have a great tech
department you can easily talk to. Ask them.
Barry
On Wednesday, September 20, 2017 3:48 AM, Edward Dunn via Fot <fot at
autox.team.net> wrote:
Excellent analysis, Dr. Dunst...
What advantage would a different gasket material have, say... copper?
Edward Dunn
President
Quality Fuel Trailer and Tank Inc.
4580 Klahanie Drive SE
Suite 423
Sammamish, WA 98029
425-526-7566 x 7012
-----Original Message-----
Sent: Tuesday, September 19, 2017 9:51 PM
Subject: Re: [Fot] Re-torquing a cylinder head - GT6
Composite Fiber gasket material has internal micro gas pockets. Depends on the
quality and repeatability of the original gasket material. When heated the gas
expands and seeps out from areas of least resistance. Perhaps after a few heat
/ cool cycles all those internal gas pockets that were present when New have
been vacated. The gasket then creeps upon itself and becomes imperceptibly
thinner. Hence the original axial tension is now reduced. Perhaps some parts
of the gasket are more inhomogeneous than others and leads to a mismatch in
"torque".
That's the nature of an inhomogeneous materials.
Anyways that's how I put it together.
Best
Mordy
MDunst Headgasket.com 626.358.1616
Fax 626.628.3777
Triple R Munitions, Inc 626.201.9471
T FFL 6,7 SOT 2
I?m adjusting valves after the last race weekend. For whatever reason, I put
the torque wrench on a couple of the head bolts - and found maybe 90 degrees of
movement on the few nuts I checked.
I run a Payen head gasket - composite with a metal ring at the combustion
chamber.
Should I:
loosen one nut at a time, lube with moly as provided by ARP, and retorque to
ARP spec; tighten from the current position to ARP spec (75 ft-lb) do nothing
The engine has probably four race weekends on it. I can honestly say I have
never re-torqued Payen gaskets before, but I have also re-checked the torque on
other gaskets and not found any movement.
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