Hi, Guy Weller...
Yes, I do remember this. And, I suspect
you may be right. But the end result in
your case is the same, Guy.
Engines, valve guides, etc. are all clearanced for a specific
application.....
this is why I went public with Jon Paschke's post on his Longman GT6
head
wherein it comes equipped with seals on
the exhaust valves.
It proves the point that while we all think
of exhaust pressurizing the exhaust port
maybe there is a "place" in the exhaust
cycle where this is not the case? Especially when stem/guide clearance
is "wide" as in "performance" or "racing"
applications in line with Chuck Christ's
prior post on this thread?
Well, I am no engineer but, in accordance
with what little I know about pressure,
temperature, velocity cycles...sure, I could
see how this might occur somewhere in
the constantly changing exhaust cycle.
Especially with "racing" clearances....
absolutely.
Longman must think so, too, as they sure
as hell wouldn't be putting seals on their
exhaust valves for no cause. You can
bet these match the "intended application"
of their GT6 head, including the "wider" stem/guide exhaust clearance
they built
into it, for sure. This head is intended as
a perfomance (track) application, after all.
and consistent high heat operation in terms of rpms and throttle
loadings. And
these consistent high operating temps.
are "closing up" those clearances and still,
these are wide enough to the extent Longman puts seals on the exhaust
valve
stems. Gotta be a good reason.
I could see how your shop may have erred
on the cautious side when going from
leaded to unleaded, especially since guide
materials for each application can be very
different.
Be that as it may, Guy, effectively and with respect to oil supply to
the exhaust
valve stem, you found yourself in GT6
type "performance" territory, clearance-wise. As what works for them
in terms of oil control in this respect, also
worked for you. The fact it was "intended"
in their use and "unintended" in yours,
is academic.
Effectively:
You got "track" clearances when you should have gotten "street"
clearances,
leaded or unleaded application notwithstanding. Yes, even the pro's
make mistakes......like you and I, Guy,
they are human. And humans make errors. That's why there are two pilots
up there and still.......
Cap'n. Bob (Ret'd)
'60 Frog
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/spridgets
|