Paper or plastic? (valve guides)

[Jon Pike <jhpike@domain.elided>]

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.

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..

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?

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

Jon
77 Spider,  engine to be rebuilt
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided