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With stock Cams and the stock non adjustable exhaust cam sprockets, the CAS should always be close to center of the bolt holes.
With adjustable cam sprockets that have been adjusted, the position of the CAS on the bolt holes can move.
Also some aftermarket cams do not have the CAS drive exactly the same as stock and this will cause the CAS position to be different also.When you set the mechanical timing, you have to know what signal the ECU is sending to the CAS. You can not assume it is 15 degree's.
If you do not get idle contact, the Cas will receive a higher ignition timing signal from the ECU. If the idle is set too high, the ECU is sending a higher timing signal also.
A neutral switch not working can send out a different timing signal. A auto ECU program in a stick car can send out a different signal, this could be from converting a auto to a stick or simply a wrong program, the list goes on.....
Many, many things can effect what the ECU sends out to the CAS for timing. You have to read the signal with a proper tool (Consult, datascan, Ect).
Once you know the signal, you match the mechanical timing to the ECU output.
If you have stock cams, stock exhaust sprockets, and your ECU output from a scan tool reads 15, your CAS should sit in the middle of the bolt holes when your mechanical timing matches the 15 degree output from your ECU.
If your CAS has to be moved all the way to the edge of the bolt holes to get the mechanical timing to match your ECU output signal, more than likely your timing belt is not on correctly if your exhaust sprockets and Cams are stock.
I have run across at least 50 Z cars over the years that had the timing belt installed incorrectly. Most of those timing belts that were on wrong were installed by large shops, many were Z only shops and Dealers.
I would say more than half of the cars I see today have the CAS adjusted incorrectly. I see them off both directions all the time.
In the recent tuning groups, only 1 or 2 cars in each group had the correct CAS setting.
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