My questions relate to a 420 SEL, 1986, Engine 116.
Due to a loud ticking noise coming from the valve cover, in the area of the #1 cylinder, I plan to remove a couple of rocker arms to inspect for wear. In researching this subject in the shop forum archives, it's unclear if the use of compressed air is required to hold the valves closed while this work is being performed. Some posts make mention of it and others do not. If compressed air is required, I'd like to know "how much pressure"?

Another question? Just based on the noise, can anyone tell me how to differentiate from the sound of a rocker arm gone bad versus a failed rocker arm and ball stud assembly?

Thanks for any response.

William