Larry,
The choice of valve guides may be dependent on the type of valve you
are running. When I ran RimFlo valves, I was told that bronze guides
were preferred for plated stainless steel valve stems, due to their
frictional/lubrication properties. On the first ported head I did
with RimFlo valves, I went with iron guides because my machinist (a
V8 hotrod guy) preferred them. I got a stuck valve in pretty short
order, and redid the head with GOOD quality bronze guides, which
worked just fine.
Bronze guides are more "finicky" than iron ones as far as tolerances
go. There are "softer" and "harder" varieties of bronze-manganese
bronze, silicon bronze, etc.-with different wear properties. I
believe the manganese ones are to be preferred, but someone may
correct me on this.
I used to get parts like this from APT
(http://www.aptfast.com/Main_Index_Page.htm), back when David Vizard
was involved in it (no interest...)
Chris
--
Chris Attias
Aptos, CA
'64 MGB
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