Chris Lillja wrote:
>
> Just had to put in my $.02...
>
> I bought a used head to dismantle and rebuild. Examining it, I have reason
> to believe that the addition of the valve stem seals contributed to the
> early demise of the guides. The valve stems with the seals weren't just
> worn, they were galled.
My guess is that, if they bronze guides, they were installed dry, or
were cast-iron guides.
That's the salient point: were they cast-iron guides? I tried to make
that pretty clear that seals weren't installed as OEM because the iron
guides required more oil.
> Precious little oil gets to the top end of a TR anyway and I wouldn't be so
> quick to discount the value of its cooling and lubricating effects on the
> valve stems and guides.
Well, I think this description is for an engine with worn-out mains and
rod bearings and tired rockers and shaft, and maybe the thrust washers
in the sump. Volume of the stock pump is adequate for SCCA. A number of
the people here have said, in the previous threads on rocker lubricating
lines, that if the bottom end is right, and the rockers and shaft and
pedestals are in good shape and installed properly, there's no shortage
of oil at the top end.
> Bottom line -- I think the engine will smoke less in the long run and the
> guides will last longer without the seals.
Without stem seals, oil consumption will be higher. Whether the engine
smokes, or not (and, very typically, oil going down the exhaust guides
won't cause smoke because of the more complete burning due to high
temperatures in the exhaust valve port), oil consumption will be higher,
especially if the engine is run at higher rpms, since more oil is pumped
to the top end.
> The bronze valve guides seem to work very well without them. I wouldn't use
> the original style iron guides in either case.
Bronze guides would work fine without seals, but because of their
composition and properties, they will work with seals, and that's the
point. Consider that almost every engine today with an aluminum head
(and aluminum heads are almost universal today) is equipped with hard
valve inserts and aluminum-phosphor bronze valve guides. And, typically,
these engines, with regular oil changes and less maintenance than needs
to be regularly performed on a typical Triumph engine, go
150,000-250,000 miles, generally use less oil in the process, and
produce more power on a hp/cc basis with leaner mixtures, so their heat
rejection requirements are higher. Why then are similar materials so
inappropriate for the Triumph engine?
I don't think it's materials used in the valves, since Kastner, in
virtually every competition guide he's written, says the standard valves
are quite suitable for racing use, and that with the seat surface out to
the edge of the valve face to enable larger ports. Most of the no-lead
kits today included the standard valve, besides.
It might be heresy to say so, but the engines in most of our cars never
had the benefit of newer technology, and the general belief, because of
that, is that the designers did the best with what was available. That
isn't entirely true, because some things, regretfully, were done to save
money. No engine today should be running an iron camshaft in bores
machined directly in an iron block, but most of ours do. That wasn't
because a cast-iron to cast-iron mating was better--it was done because
it was cheaper. I submit a similar case can be made for valve equipment.
Cheers.
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