1. I THINK that it was 5.1 mm.
2. In my opinion, these are generally OK as they are unless:
a. You had the head shaved (not recommended)
b. Valve/head work has deepened the valve pocket a little, thus raising the valve a little
c. You changed the hydraulic compensator and it didn't thread exactly like the old one
3. There is an oil drain groove in it, so machining would NOT be good, it is also probably case-hardened.

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86 560SL
With homebrew first gear start!
85 380SL
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