The MB manual for the 380sl, which has the 116.690 engine, explains rather briefly that the relationship between the engine's valves and cams can be adjusted by:

1) Placing a movable pin of a specially designed go-no-go gauge over the rocker at the lifter when the corresponding cam lobe is up,

2) Determining how far a line in the center of a 1.1mm notch on that pin deviates up or down from a line determined by the measuring edge on the gauge, and

3) Replacing the existing shim with a thicker or thinner one, thereby bringing the first line closer to, and ideally in line with, the second.

My questions are:

1) How far off from the gauge's measuring edge should the movable line be before a shim change is warranted?

2) Can the thickness of the replacement shim be calculated by measuring the distance between the gauge's measuring edge and the pin's movable line? For instance, if the movable line is, say, .25mm above the measuring edge, does that mean the the replacement shim should be .25mm thinner than the existing one?

3) Can a too thick shim be reliably ground down to the correct thickness, or should new ones always be used?

3) What is the thickness of the original shims on the 116?

Thanks very much in advance for any answers anyone can give me to to these questions , and for any additional info on the best way to measure and replace valve shims.