Twing, B18CEG is correct in what he is saying. If the strap is under the dome nut it is in fact earthing the head. Via going through the stud to the head. If the strap is in that spot it is acutally insulated from the Rocker cover via a rubber washer. ie theres no connection to the rocker cover.

But the 1st post topic, states:

Quote Originally Posted by claymore View Post
whether or not any engines rocker cover NEEDS to be grounded NOT JUST GROUND WIRES INSTALLED ON OR NEAR THE ROCKER COVER BUT METAL TO METAL CONTACT BETWEEN THE ROCKER COVER AND GROUND THROUGH A WIRE FOR THE PURPOSE OF CURRENT FLOW THROUGH THE ROCKER COVER.
The strap on my B18C7 is actually on the rocker cover itself. Not under a dome nut. The same goes with my B16A2 delsol. In that case its only earthing the Rocker cover. I have seen may other like that too.