re: (valve guides)

[Jay Negrin <jmnegrin@domain.elided>]

From: Jon Pike
Subject: Paper or plastic?  (valve guides)

I've been wondering the relative merits of different valve guide
materiels,  i.e. the silicon-aluminum bronze that Sperry uses in their
rebuilt heads,  vs the manganese bronze that IAP and others use.

--uranium-phosphorus?  I'll let the pro's handle this one....

Of course this leads to other comparisons,  of differing places doing
your head work..  and I know that the Digest discourages such direct
comparison.  So if anyone had some "input" about it,  letting me know
off Digest would be appriciated..

--no help here either...

Hmmm..  as for some more on topic, in Digest fodder..  how about sodium
cooled exhaust valves as opposed to the newer (assumably better heat
transferring?) alloy ones?  And how do you know the ones in a catalog
are sodium cooled,  if they don't say so?  Price??  I've seen $13 and
$40 exh valves..  that might be a clue?

--$40?  Sounds  like sodium-filler valves to me.  I would think that
they would be superior to mono-metal valves for heat dissipation, which
is why you go that route anyway.  Titanium and other wonderful alloys
might be lighter, but if you aren't revving the 'whee' out of the motor
( i.e. racing!) then I don't see much benefit.

Prepping myself (hopefully) for my head work,  and what to do if they
say "ya need a few valves"..

--If you need a few, just spend the bucks and get a whole new set.
FWIW, when I had my head done some years ago, my mechanic said that the
exhaust valves were OK, and the intake (non-sodium filled, as the intake
charge cools them, somewhat) were the ones in need of replacement, which
I did.

Jon
77 Spider,  engine to be rebuilt

Jay Negrin
76 Alfetta GT - only the head, to date.
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