this is what i had to say a few months back and see no reason to change my
view................
**********************************************
in our engine shop, we avoid bronze guides unless we really have to use
them such as with some specially coated titanium valves
cast iron guides last for a very long time under very arduous conditions
about the only OE manufacturer that I've seen that routinely uses a bronze
guide is M Benz, and they are a very special product and only used in some
of their engines
not all bronze guides are equal. we have encountered numerous grades. all
of them are notoriously difficult to size. we have special tooling to deal
with them.
there is an argument that some types of bronze guides can run lower
clearances and therfore improve heat transfer from valve stem to guide. i
have never seen any documented or visual proof of this .
IMHO, especially with older cars like TR's, they are mostly a marketing
fad, with unscrupulous vendors appealing to the 'go faster" set
*****************************************************************************
there has been some mention in the posts over the last week of bronze guide
liners. these are still very common with budget priced rebuilds , with the
american K-line brand being very common, and especially good for some
american V8's where the guides are not removable. whilst we use
them occasionally, we use cast iron "sleeves" (called thin wall guides)
where possible to repair these types of heads.
if we have a metallurgist amongst us, then some real advice on bronze guide
composition would be good.
my challenge to all the readers of this subject is for someone to
demonstrate some real world benefits in old engines, over an above a
properly fitted & reamed cast iron guide .
Terry
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