Re: [Amc-list] Oil to Use: It must be rated for 'Diesel'

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: Tom Jennings <tomj@xxxxxxx>
" 
" I dunno about this oil stuff... is this one of those things like the lack of 
" lead causing excessive valve wear? I know there's actual chemistry involved 
" with the lube business but I've never heard of any of our engines dying from 
" oil related issues.

it's happened.  go over to strokers@yahoogroups and ask about cam
failures...

" The lead/valve wear thing turned out to be a crock and it's hard to get worked 
" up about this oil thing.

http://www.lnengineering.com/oil.html for a start.  somewhere in the
twisty maze of urls starting at the bottom of that pg i tracked down
the '77 sae paper he mentions, and in it they set the old zddp levels
by observing cam and lifter wear on production engines.  so no, it
isn't snake oil.

the recent flap was set off by muscle car owners and old car folks
like us who've been seeing premature cam lobe failures, ultimately
traced to low zddp levels in modern oils.

it appears to be a problem only for folks running flat-tappet pushrod
engines and has something to do with valve spring pressures.  ohc
engines and roller lifter engines aren't subject to it.

anecdote: mopar went to low-tension 'beehive' valve springs on
late-ish 4.0s, presumably to try and cope with low zddp levels, but a
local jeep mechanic who's old enough to have a touch of gray and a
limp says they're crap and whenever he has a problem with them or
traceable to them, he replaces them with the older style springs.
i'll have to ask him if he ever has comebacks with cam failures next
time i see him.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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