The lifters will, in fact, normally bleed down a little bit (sometimes
alot!) when left not running overnight or for a few days or so.  Yes, it's
not a perfect seal (neither the lifter piston/ cylinder walls, nor the check
ball), so some oil does escape by seepage.
  I've driven bay window busses and Vanagons, both air- and water-cooled,
with high mileage engines, and they've always had a bit of lifter clatter
when first starting them up after a period of sitting.  My newer WBX has
never clattered yet, I suspect it's due to being a low mileage. all original
engine.
  That flat-four configuration is famous for having this trait.

YMMV,

Mike B.

>
> A follow up question is, just how do the lifters "settle" after pre-
> loading them?  The only way the piston can drop further into the lifter
> body is if some of the oil located in the valve body, but below the
> piston, is removed.  As long as the check valve on the bottom of the
> piston is working, the only exit route for this oil is between the inside
> wall of the lifter body and the outside wall of the piston, ultimately
> exiting the oiling oil on the side of the lifter body.
>
> It is tempting to manually remove some oil from the lifter body so that
> when they are adjusted to +1 there is enough give to prevent the valves
> from opening.  Then run the motor and let them "pump up" to the proper
> height.  I suppose this risks trapping air in the lifters resulting in the
> performance problems Bob refers to in his "history of hydraulic lifters"
> article.
>
> Yeah, I know, beating a dead horse and all.  I have read the heck out of
> the archives and I still don't get it.
>
> jake
> 82 AC Westy
>