>I have noticed that I hear something that sounds like faint valve clatter
>coming from the engine of my '85 GL.  This happened once before and
>disappeared, now it's back.  I hear the noise while accelerating and
>cruising but NOT at idle.  I figured if I had a stuck valve, that's when I'd
>here it--no valve noise on starting up (like in my '85 Jetta and '92 Passat).

It's a sticking hydraulic lifter, or more likely slightly collapsed.  When 
you accelerate the loads on the valve train increase, due to inertia and 
combustion chamber pressures. At cruise you are still under higher loads 
than idle. Hence the ticking.  Try an oil change, go to 20W50, if it's not 
going to be cold your way! That usually works fine.

         Has anyone with synthetic oil ever experienced this problem?
        
        I have the same problem now if I let the van stand for 4-5 days, due 
to winter 10W30 oil just installed.

*** List question???   Has anyone tried Bardahl valve lifter additive for 
this problem.  The VW service manager here 'off-the-record' said they put 
about 1/4 of container in to quiet things down. Don't know the container 
size nor exact sort of Bardahl product.  He was quite explicit about using 
VERY little.  Any net wisdom here?