[quote=datsun280z;1343487The problem accures when the engine is hot and in idle.. the
engine starts to vibrate ... even strong vibrations until it shuts down
[/QUOTE]
Bump your idle speed up a bit. The book says something like 650rpm's. But that's for a bone stock engine. Aftermarket heads, cams, carbs, etc, usually require a higher speed. I'd go to 850-900 and see what happens.
If you're running something rediculous like a Holley Dominater and a Victor intake, you might have to go to 1,100-1,200.