At 12:03 AM 2/1/2000 -0600, John Rodgers wrote:
>David, from what I know about hydraulic valve lifters, you are pretty much
>right
>own. Most of my experience is with aircraft engines and they work the same
>way.

>http://precisionengine.home.mindspring.com/engine3.htm

You'll be interested in this and related pages...

>correctly...and its been a long time since I went through this....there is
>a basic
>"lash" setup clearance for engines that have had the valve ttrain worked
>on or had
>lifters replaced. Once that clearance is set, proper operation of the lifter
>piston inside is all that is needed for the valve train clearance to
>adjust itself
>to zero clearance.

Right.  That adjustment shortens the fully extended lifter so that it has a
range of operation in both directions.  The trouble is that on *some*
rebuilt Vanagon engines (like mine) that same adjustment lowers the
compression, indicating that the valves are not fully closing.

>As for horizontal operation being a problem, I wonder. Witness the horizontal
>aircraft engine. They don't have air entrapment problems with the lifters.

I don't personally think it's a great problem.  I have personally assembled
and bled a lifter, installed it in an engine, had it get flabby while in
the engine, and then had it work the bubble out by itself and become
rock-hard again.  I don't know the timing, though -- it had been in use for
some days when it was observed to be soft, and it was some days later that
it was hard again.  There's some discussion of air in mushroom-type lifters
on the Lycoming page I cited above.

*However* -- it has been observed by many that using an oil filter without
an anti-drainback valve often leads to excessive lifter noise on startup,
so to that extent I reckon it's a problem.

As far as I'm concerned the real problem is whatever is causing these
hydraulic lifters to act like solids.  And I hope to find out this
spring.  As you so correctly point out, the major reason these things exist
is so you can just set them up and walk away.

cheers
david

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"