X-Mozilla-Keys:                                                                                 
Ed Anderson wrote:

 Paul, I just went back out to the shop for another look.  The set screw is
actually centered in a boss between the trailing plug and the prepherial
surface of the housing (not the edge that faces the end and intermediate
housings)..  So it is not a racer mod thing but cast in the housing at time
of manufacture.  The line from lead to trailing to set screw is a straight
line.

Just curious about its function, I guess I could unscrew one and see if
coolant leaks out.

Ed

"the prepherial surface of the housing (not the edge that 
faces the end and intermediate"

By this I think you mean the top of the engine.

You got me. It does'nt sound like the knock sensor boss.
There is no need for a screw in plug in the knock sensor boss.
What size is that set screw? Could be Mazda decided to put a plug
in there. You might have some post 1993 rotor housings with
the knock sensor bosses. When you bought a new one did you show 
them the old one? Maybe all replacement rotor housings are 
the late type.

Paul Lamar
 
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