Is your crankcase overfull? Proper oil level is midway between the two marks.  When I had a 1.9, if it was to the top mark, after about an hour at freeway speeds, the oil would become so aerated that it would lose pressure, the lifters would collapse and all the power would go away.  

Sound familiar? Try lowering the oil level a pint or two.

Good luck.

Jim

> On Jun 5, 2016, at 12:46 PM, Wrenold Williams <wrey455@YAHOO.COM> wrote:
> 
> Question:  Where can I purchase eight Febi Valve Lifters - the ones with the
> sturdy c-clip holding the parts together? I understand they are the better ones!
> I currently have the ones with the paper clip holding the parts together.
> My 1984 1.9  Westfalia starts & runs fine with no valve noise but after driving for about
> an hour at 60 - 70 mph or so then the engine loses power and the valves become very
> noisy.