617.95 Valve clearances

[Volker]

Hi guys

I have a couple of broken, in disassembly 617.95 engines and a car. I think an '85 that made smoky and a '82

What happened to the 1982 engine was that it snapped the cam towers and camshaft (!) Replacing them resulted in snap again.

I wonder what is going. Perhaps the valves being not quite tight, but somehow kept open and the cam needing to force against the slammed spring.

Presently I have cam tensioner guide broken and needing removal, but the dowel pin seems to be keeping it in. How to remove?

Are there any other suggestions for what may have caused failure?

Thanks,