having read a number of confusing and conflicting info on cam specs for
the old d-series motors saying that the si cam and zc cam are the same,
i have done some homework, namely acquiring cams from all 3 of the main
motor types, and have measured the cam specs accordingly:

model cam° lift-mm
dx in 152 5.56
ex 166 4.66

ex/si in 156 5.74
ex 166 4.94

zc in 164 5.92
ex 168 4.96

note:

1. these are direct measurements taken with the cam out of the motor -
not trying to measure in the motor via a rocker arm or crank shaft.

2. the zc cam was removed by me personally from a genuine jdm sohc zc
motor, so it is authentic.

conclusion: the zc and si cams are /not/ the same.

the reports i've read where other people have measured no differences
seem to be because some individual on e-bay has been ripping people off
selling si cams as a zc's - possible because there are no distinguishing
marks between the two other than direct measurement of the cam profiles.