"Clacking" from the footroom, "sleep", measuring rod?

Hey, guys!

So I often hear a strange "tackern" or "kackers" from the driver's side footroom in my 90s 3,6l V8.
It does not occur regularly and the interval is not always the same, so once faster and once slower.
It only occurs with the running engine, with the air conditioning it also seems to have nothing to do, because it is still to be heard in the "off" position.
What can that be? Sounds similar to switching a relay, just louder and often in a row...

Furthermore, I imagine that my V8 is quite slightly ruptured when accelerating under full speed. It is hardly noticeable and about as if a slight "slip" in force could be heard.
What could this be related to? ==References== 230tkm down....

One more question I have: Why is the measuring rod with the red handle, which is about 30 cm behind the oil measuring rod (oranger Henkel)?

So, that's it, too.

Thank you so much,

Greetings Roland...