Here is something interesting that happened to me.
I always had lifter noise on startup in my '91 Vanagon with 166k miles.  I
added 1 quart of ATF to oil (after draining a quart) and ran for a few days,
then changed the oil and this helped for a while, but then the tapping came
back as the next oil change approached.
Then my van blew the head gaskets (see archives for this story).  Upon
removing the valve covers I saw my engine was very nasty inside (much gunky
looking oil, etc under the covers).  I removed and throughly cleaned the
rocker arms and push rods (spraying through them with brake cleaner) and put
it all back together.  Since then, no lifter noise!  I am wondering if maybe
one of the push rod tubes was clogged and not allowing the oil to flow
properly, etc.  I don't know exactly why but this has fixed my tapping
permanently (as permanent as you get with the waterboxer anyway).
Just thought I would share.

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
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