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:
- 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.
- 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.