I remembered
when I first installed the HKS adjustable cam gears, I've said
that if one day I couldn't resist the beauty of exposing the cam
gears, I would have the front part of the valve cover mutilated
to nicely expose the adjustable cam gears and ease cam timing
adjustment.
This day
has come since both Terence's '90 Red and our friend's '90 Blue
had their valve covers mutilated to nicely expose their
adjustable cam gears, I finally decided it's time to expose mine
as well. The front part of the valve cover (as in the other two
miatas as well) was nicely machine-cut as shown.
While I was waiting for Terence and Alfred working on other
miata stuff in the machine shop for the rest of the afternoon, I
took the opportunity to hand-polish the valve cover. After
rinsing the valve cover and dried, I started sanding with #240
abrasive paper. Less than an hour later, it's good enough to
switch to #400. It took longer for the #400 to get an even
surface. About an hour or so later, I switched to #600. The finer
the paper, the longer it took to finish the entire surface. 
I probably
spent 2 hours with #600 paper, partially becauase I concentrated
on areas like the curves at the very front of the cover and the
areas near the PCV and the other vent fittings, and partially
because I had to wait for Terence and Alfred. After we got home,
I used some alumimum polishing compound and polished the valve
cover to mirror-shine. See the reflection of the front engine
hanger eye on the valve cover just below the engine oil filler
plug in the left picture?
Of course the exposed cam gears would not affect performance. The cut valve cover is just for looks and facilitates adjustment.
Next: 
Intake system
