Date:         Wed, 19 Mar 2003 06:28:34 -0800
Reply-To:     pensioner <al_knoll@PACBELL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         pensioner <al_knoll@PACBELL.NET>
Subject:      Re: cam breakin'
In-Reply-To:  <200303190508.h2J58Ckv000293@mtac1.prodigy.net>
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Laurasdog spake...

The 2000RPM for 20 minutes thing is all about cam/lifter break-in.
The cam and lifters want LOTS of oil until they get somewhat seated in to
each other. One of the worst things you can do is let an engine idle
a lot during cam break in. Those first few minutes of a cams operational
life determine a lot about how long it will last...

To which I mumbles ...

Perhaps, perhaps not.  The camfaces are hardened, polished surfaces.  The
followers are hardened polished surfaces.  The lubrication method is splash.
There is no "sealing" needed as there is in the ring/liner interface.
Nikasil liners and piston rings knead close tolerances to function
effectively as a seal.  Cam-follower interfaces only need enough lubrication
to prevent galling and micro-welding.  Roller-tappet cam systems are
designed to deal with high spring pressures that allow valve float to be
postponed until higher rpm and avoid the galling - welding failure that
would occur in a sliding contact interface as found in non roller systems
like ours.

I fail to see on a fine-structure basis how "seating" the cam to follower
interface can materially affect it's life.  Good builders will often put a
suitable amount of assembly lubricant on the cam face to avoid the first few
seconds of operation without proper lubrication.  After that the abrasives
held in the oil and the lubricating properties of the oil dictate the
scuffing wear.  Doesn't seem to have much to do with "seating".

I'm not a tribologist but I often play on the tv.