I work as a service writer for a small shop in town, and had the guys do some work on my car today. When they tried to check the timing, they were a bit confused. I have a 95 LT1 TA with the MSD OptiSpark, and there's no timing marks. I tried to do some research online, but all I found was that you can adjust timing with a screwdriver... not much help. Can anyone give me any info to give these guys?

Thanks,
Amanda

 

Unless you have an MSD aftermarket OptiSpark, you can't manually adjust the ignition timing on the LT1 engine. There is a optical cam position sensor inside the OprtiSpark distributor. This tells the PCM where the cam is in its rotation. The PCM looks up the desired timing advance in a table with RPM on one axis and MAP on the other, makes offsets for various operating conditions, like inlet air temp, and then uses the cam position to calculate when to fire each spark plug (and also each injector - 94-97 only). It sends a pulse signal to the Ignition Control Module (ICM). The ICM is the "switch" that tells the coil when to fire.

To change the ignition timing, you must make the changes to the tables in the PCM. There is no way to verify actual timing externally, because as you discovered there is no indicator on the damper.

The MSD Opti allows you to adjust the timing +/- about 5-degree, but there's really no reason to do that unless you are compensating for a cam that has been advanced or retarded.

If you are trying to "retard" timing for something like nitrous or boost, there are external boxes that allow you to do it.